The Porsche 718 Cayman is meant to represent one of the more affordable entries into the world of exotics; however, with a nearly $75,000 starting price, the car is still all but inaccessible for many enthusiasts. Thankfully, there are a number of alternatives that can provide similar thrills and driving dynamics without breaking the bank. Of course, these vehicles don't necessarily replicate the pedigree of a Porsche, but they come surprisingly close in terms of performance, and they'll make the feeling of keeping up with a Cayman all the sweeter.From sporty German roadsters to classic Japanese coupes, there are many options for those who want to experience the excitement of a true performance vehicle without the associated Porsche price tag. We've looked high and low to find some of the cheapest out there, considering only bona fide sports cars in our efforts to guide you towards affordable driving enjoyment. 2013 BMW Z4 sDrive35i Used Price: $18,978 - $20,201 Bring a Trailer2013 BMW Z4 sDrive35i SpecsAlthough the E85 generation Z4 allows for more affordable BMW fun, it's a touch too slow to make a compelling alternative to the Porsche 718. For this reason, we'd suggest going just a little newer with a 2013 example from the E89 series. In particular, we'd advise the sDrive35i, as the 3.0-liter turbocharged inline-six is good for 300 horsepower and 300 lb-ft of torque – that's more than enough grunt to power the car to 60 mph in five seconds or less. Assuming that's not quick enough, there's always the Z4 sDrive35si; MotorTrend managed a 4.4-second 0-60 sprint thanks to the on-demand boost. However, it'll take some patience to find one for less than $20k – with enough searching, you'll see that the si typically averages closer to $30,000.In any case, if you like the feel of the wind in your hair, it's hard to go wrong with a Z4. The BMW has become synonymous with the roadster segment for a reason; it's earned a reputation as one of the best convertibles (used or new) you can buy today. 2013 BMW Z4 sDrive35i Sales Classic.com Average Sale: $20,201 Classic.com Most Recent Sale: $16,250 2010 Audi TTS Used Price: $15,222 (Coupe) | $15,867 (Convertible) Cars & Bids2010 Audi TTS Specs If you’re after German build quality, but you can’t stomach the price of Porsche’s Cayman, never fret – this pick from Audi should do just the ticket. A step above the standard TT, the S-spec coupe comes powered by a turbocharged 2.0-liter four-cylinder engine good for 265 horsepower and 258 lb-ft of torque. Because the TTS comes with Quattro all-wheel-drive, this translates to a very capable 4.8-second 0-60 mph sprint – even when mated to a six-speed dual-clutch gearbox.From a styling perspective, the second-generation TT skews much more like the Audi R8 than its predecessor. The angled headlights and grille, the roofline, and even the spoiler all give it the air of a scaled-down supercar. 2010 Audi TTS Sales Classic.com Average Sale: $13,321 Classic.com Most Recent Sale: $5,300 2001 Chevrolet Corvette C5 Used Price: $15,186 - $24,779 GM2000 Chevrolet Corvette C5 SpecsChevrolet’s C5 Corvette makes for one of the better ways to get cheap speed, and this proves especially true when looking for affordable Cayman competitors. Though the 20-plus-year-old American won’t have the same tech as a modern German coupe, it’s still a very proficient machine through the twisties, and it’s capable of some compelling straight-line performances. Even for the base model, 0-60 mph comes in 4.8 seconds; assuming you want to race Porsches with more authority, the Corvette Z06 will shave a further half second off that time.Along with some immense torque, the ‘Vette also brings a healthy dose of retro styling. You’d have to go much older to get pop-up headlights in a Porsche, and it certainly wouldn’t be able to keep up with a current Cayman. 2000 Chevrolet Corvette C5 Classic.com Average Sale: $19,931 Classic.com Most Recent Sale: $28,000 2005 Mercedes-Benz SLK 55 AMG Used Price: $13,685 - $22,777 Mercedes-Benz2006 Mercedes-Benz SLK 55 AMG Specs Depreciation tends to hit used Benzes pretty hard, making even AMGs affordable secondhand. Of course, be sure to do your research – you don’t want to be taking on a vehicle that’s expensive to maintain. The SLK 55 AMG ranks among the cheaper Mercs on the used market today, and this means that you can stand to get some very potent performance for the money. The naturally aspirated 5.4-liter AMG V8 puts down 355 horsepower and 376 lb-ft of torque, enabling a 4.5-second 0-60 mph sprint and a 13-second quarter-mile.Even though this Mercedes-Benz is going on 20-plus, it still makes for a luxurious interior experience with plush leather and a central infotainment system. With SLR-like looks and raw AMG power, it’s a decidedly brawnier option than Porsche’s 718 Cayman. 2006 Mercedes-Benz SLK 55 AMG Sales Classic.com Average Sale: $22,577 Classic.com Most Recent Sale: $13,000 2010 Nissan 370Z Used Price: $12,132 - $19,267 Nissan2010 Nissan 370Z Specs Nissan’s new Z is pretty pricey to justify for anyone but the most hardcore of enthusiasts. Thankfully, the older 370Z can give you much of the same fix for about half the price. The naturally-aspirated V6 made 332 horsepower and 270 lb-ft of torque, and the car could be specced with either a 7-speed auto or a 6-speed manual. On the road, this translated to some impressive performance for the day – MotorTrend clocked a 4.8-second 0-60 in the 370Z roadster, making the coupe a few tenths quicker still.The 370Z is a car that every gearhead should drive, especially if you consider yourself a true JDM fan. 2010 tends to be the cheapest on the used market, but it's possible to find some newer examples for similar prices. 2010 Nissan 370Z Sales Classic.com Average Sale: $19,267 Classic.com Most Recent Sale: $7,700 2004 Pontiac GTO Used Price: $12,102 - $19,083 GM2004 Pontiac GTO Specs Because of its subdued styling (certainly compared to its predecessor), the 2004–2006 Pontiac GTO tends to fly under the radar for anyone but those in the know. Still, what the Holden-based coupe lacks in aesthetic appeal, it more than makes up for in raw performance. Under the hood, GM fitted the car with a Corvette-sourced 5.7-liter LS1 V8 for the 2004 model year. Though it’s slightly down on power compared to the 400-horse LS2 of 2005 and 2006, that also means that it’s a slightly cheaper buy. 2005 and 2006 Pontiac GTOs each average over $20,000.0-60 mph times vary from publication to publication, but all reviews have Pontiac's modern GTO putting down a 5-second sprint or quicker, and Car and Driver even managed a 4.8-second display. If Porsche-beating performance is what you’re after, the LS2 is worth the premium. The upgrade brings more displacement, more power, and more torque. 2004 Pontiac GTO Sales Classic.com Average Sale: $19,083 Classic.com Most Recent Sale: $7,000 2005 Chrysler Crossfire SRT-6 Used Price: $9,068 - $17,270 Bring A Trailer2005 Chrysler Crossfire SRT-6 Specs If you think that the Chrysler Crossfire looks similar to the above Benz, there are more similarities than mere appearances. As a product born out of the Daimler-Chrysler union, the Crossfire featured as much as 40% Mercedes parts, and it shared its platform, suspension, and drivetrain with the SLK. With the up-spec SRT-6, Chrysler opted for an AMG-sourced supercharged 3.2-liter V6 making 330 horsepower and 330 lb-ft of torque. On the road, this made the Crossfire an incredibly quick car, especially for the day. 0-60 mph in 5 seconds is easily achievable, and we’ve found several accounts boasting even quicker times.Unfortunately, the manual wasn’t available as an option on the SRT-6, and the performance-focused suspension means that the car can ride a touch hard. However, if you’re after a domestic sports car with European flair, the Crossfire can’t be beat. 2005 Chrysler Crossfire SRT-6 Sales Classic.com Average Sale: $17,270 Classic.com Most Recent Sale: $9,900 2008 BMW 135i Used Price: $8,103 - $16,041 Bring a Trailer2008 BMW 135i Specs BMW's 3 Series remains the gold standard in performance sedans, but we wouldn't recommend it to those wanting a sports car. Instead, we'd suggest its little brother, the BMW 135i – you're getting the same twin-turbocharged inline-six as the 335i, albeit in a much smaller package. BMW shaved some four inches from the 3 Series wheelbase and as much as 8.4 inches from its length to arrive at the compact 1 Series. The weight savings make for a quick performer, too, as 0-60 mph comes in a mere 4.7 seconds.Because BMW enthusiasts recognize the appeal of the 135i, you'll find that Kelley Blue Book's Fair Purchase Price can be a little optimistic. However, even Classic.com prices tend to fall well under $20,000 for the 2008 model year. The average sale comes in at $16,041, and the most recent example sold for a mere $7,150. 2008 BMW 135i Sales Classic.com Average Sale: $16,041 Classic.com Most Recent Sale: $7,150 1992 Mitsubishi 3000GT VR4 Used Price: $5,942 - $16,695 Mecum Auctions1992 Mitsubishi 3000GT VR4 Specs Beyond being the oldest car on this list, the Mitsubishi 3000GT VR4 is also one of the most underrated. And it’s a shame, because the car deserves just as much appreciation as other more well-known Japanese classics like the Mazda RX-7 and . Beyond a rally-sourced all-wheel-drive system, it boasted innovations like electronically controlled suspension, cockpit-adjustable Active Exhaust sound control, as well as automatically-adjusting front and rear Active Aero spoilers.On the road, the twin-turbo 3.0-liter V6 could rocket the 3000GT VR4 to 60 mph in as little as 4.8 seconds. Though the second generation from ‘94 onwards adds a bump of about 20 horsepower, the 1992 model makes for a more affordable buy. 1992 Mitsubishi 3000GT VR4 Sales Classic.com Average Sale: $16,695 Classic.com Most Recent Sale: $33,500