THESE performance cars have slipped under the radar - and unfairly so.

The word 'underrated' and 'performance cars' don't tend to go hand-in-hand. They're the types of cars adored by petrolheads - and even those not actually that interested in cars - across the world.

Many get a reputation far above their actual capacity (looking straight at you, E46 BMW M3) and almost all have a contingent of die-hard followers. That said, some slip under the radar - and perhaps undeservedly so. Here's what we think are seven of the most underrated performance cars ever made...

1. Nissan Skyline R33 GT-R

Adding a Nissan Skyline of any kind to a list of 'underrated performance cars' might seem ludicrous, but bear with us. The R33 Skyline is something of an ugly duckling in the legendary Japanese machine's family history. The R32 before it held all the motorsport glory, even earning the nickname 'Godzilla' as a result, while the succeeding R34 found fame as the face of video game franchise Gran Turismo, while also being an icon in the Fast & Furious film series.

Meanwhile, relatively speaking, the R33 never found much fame, often disregarded as the 'mid-life crisis' for the Skyline, despite carrying over the magnificent RB26 engine from the R32 and wrapped it in an enhanced chassis and a lower drag body. However, a gentleman's agreement between Japanese manufacturers to cap power output at 276bhp on all cars meant the R33 never filled its true potential. It remains a seriously capable machine in its own right, and with prices rising for all Skylines, now might be the time to invest in this sleeping beauty.

2. Porsche 718 Boxster

The Porsche 718 Boxster (and its Cayman sibling) were practically written off from the moment they were revealed. Former versions of the car utilised free-revving, naturally aspirated straight-six engines. Then came the 718 twins, which replaced that much-loved recipe with a turbocharged four-cylinder unit. 'Sacrilege', cried the purists, and that along with the car's already-existent reputation as a poor mans' 911, doomed it from day one. In reality though, the 718 is one of the most capable machines on the market, offering a hard-to-match driving experience in a stylish and quality package. We wouldn't say no to the return of a six-cylinder engine, though...

3. Ford Mustang EcoBoost

We'll be the first to admit that a Ford Mustang isn't really quite right if it doesn't have a snarling V8 engine underneath the bonnet - but what can't be overlooked is just how good the four-cylinder version is. Using the same 2.3-litre turbocharged four-cylinder engine from the widely-adored Focus RS - here tweaked to suit the muscle car - the EcoBoost might be the thinking man's Mustang, and certainly makes more sense on paper in the UK. It's no slouch - with 286bhp and 440Nm of torque - and that power is more usable everyday than the 5.0-litre V8s, while also delivering markedly improved efficiency figures. If you can get past the lack of an eight-cylinder burble, the EcoBoost Mustang might just be a smart choice to make.

4. Audi S1

Amidst all Audi's RS variants, the plucky 'S' models often get left behind. Perhaps the biggest victim of this is the S1. When people think about supermini-based hot hatches, they all go screaming to Ford, Renault and Mini for their renowned hatches, but the poor Audi S1 seems to end up being nearly entirely forgotten. Granted, it may be a bit long in the tooth now and overdue a good refresh, but even four years into its model run - or eight years if you think of when the A1 first reached showrooms - it still has a better, more luxurious and refined interior than some all-new hot hatches. And with 228bhp on tap from its peppy 2.0-litre petrol engine and Quattro all-wheel-drive, it puts in a unique position for a supermini hot hatch. Add in the fact it's available as a three or five-door hatch and can get from 0-60mph in under six seconds, and it seems even stranger that the S1 gets unnoticed. Yes, it might be expensive new, but there are some cracking examples on the used market from as little as £15,000. Take that, Fiesta ST.

5. Hyundai Coupe

The Hyundai Coupe never really set the world alight - and we won't argue it should have done - but it's definitely one many forget when it comes to compact sports coupes. We think a lot of this has to do with its looks. You'd be forgiven for taking a glance at the South Korean machine and expecting there to be a punchy turbocharged engine sending power to the rear wheels. In reality though, the most potent models featured a sluggish V6 engine developing a mere 162bhp - poor at the time, let alone by today's standards. What few know, however, is that it's a pretty capable machine in its own right, offering good driving dynamics and, thanks to little mainstream attention when it was on sale new, prices on the used market are pretty low, making this is a bit of a performance bargain.

6. Volvo V60 Polestar

It's certainly impossible to miss the Volvo V60 Polestar - after all, despite being a sensible estate car, it's fitted with massive 20-inch alloy wheels and painted in an eye-catching shade of bright blue. It's far from the standard V60, having been breathed on by Volvo's in-house performance arm, Polestar - it features one of the world's most powerful four-cylinder engines as well as virtually limitless traction courtesy of four-wheel drive. So if the Polestar is that great, why don't people buy them? It may be the car's image. Though Volvos are becoming cooler and hip as time goes on, the old V60 has a certain whiff of antiques dealer about it - even in Polestar Blue.

7. Vauxhall Astra VXR

The Astra's abilities are only underrated by some of the population - for many, fast Vauxhalls are near-perfect, and those people won't need any persuading. Others may need coaxing past the car's almost comically 'chavvy' image or require reassuring that the legendary torque-steer and, let's say, difficult handling won't be an issue on the road. All this is true, and while the Astra VXR is nowhere near as poised as rivals such as the Golf GTI, it's incredibly fast, surprisingly decent to live with, and - importantly - an absolute bargain on the used market. Being unpopular has its plus points when it comes to buying used.