In the rarified world of performance cars, one rule has existed since, well, forever — the Porsche 911 is the standard against which all others must be measured. I’ve driven a few 911s in my time, in various iterations, and I know why the punters go all wobbly-kneed about these iconic German machines — they’re fantastic to drive, almost impossibly so. For decades, the boffins at the company have designed and produced 911 after world-beating 911, almost at will — it’s almost as if they have a finger on a pulse that nobody else knows about. Either that or they put something in the water over at Zuffenhausen, Porsche’s HQ, just outside of Stuttgart. The thing is, Mercedes-Benz has its AMG division in Affalterbach and its principal plant in Sindelfingen, both near Stuttgart, and it looks like the water supply is finally being shared — enter the new AMG GT S.

The GT S is the spiritual successor to the wild-but-flawed SLS AMG (it will be cheaper, hence the spiritual specification) which, in its gull-wing door avatar, was possibly the most striking supercar on the planet. The SLS was essentially one huge bonnet which suddenly ended with a pert backside — some likened its shape to a cigar (a very fast one). The GT S, on its part, isn’t especially memorable when you look at its photographs; only when you stand before one do you begin to realise that it’s very easy on the eye. The cues from its forebear are immediately apparent — the same never-ending bonnet (albeit shorter in length), a delicate rise as the bonnet gives way to the windshield and roof and then a sweeping downward movement to the svelte arse.

The derriere in question has been the subject of some debate since the GT S’s launch, and with good reason — there’s an unmistakable resemblance to that of the 911, when viewed in profile. Be that as it may, there’s no doubt that the GT S is a much more lithe, taut and, indeed, sexy car than the SLS —  I certainly wouldn’t evict it from my bed.

Lined up against the rest of its stable mates in the performance and supercar club, the GT S will be more than capable of holding its own in the visual department. Indeed, as I was heading down the coastal road from San Francisco to Carmel in the GT S, a gent in the new Corvette pulled alongside, ran an appreciative eye down its length, gave the thumbs-up and drawled ‘Nice car.’ The Corvette is quite a looker itself, so that was high praise.

Manoeuvre yourself into the low-slung cabin and you’ll find a snug, sporty space — all sportscar, no mucking about. The powered seats grip various parts of your upper body firmly, with minute adjustments possible — if you’re flinging the car about at a racetrack, the side bolstering can be set to ‘vice-like’. Mercedes has really upped its cabins in the recent past, and while the GT S is no S-Class, everything smacks of quality, down to the last detail. There’s also enough leg and head room for all but the NBA’s finest, so space isn’t an issue.

The steering wheel feels meaty in the hands, and the crucial controls relating to suspension and transmission settings, ESP and so on are placed right next to the transmission lever – driver-focussed, as I mentioned. The only quirk is that the lever is set rather far back, because of the cup-holders; it’s true that Americans feel orphaned without a coffee cup or two in their cars, but this particular car would be better off without those holders. There’s been more than a cursory nod towards practicality — behind you is a pretty decent boot, with enough space to accommodate a weekend’s soft luggage for two.

Screw the cabin, though — you’re not going to buy one of these in order to envelope yourself in sinful luxury. That engine Start/Stop button beckons seductively for you to press it without delay, and press it you must, in order to fire up the 4-litre, twin-turbocharged, hand-built V8 engine, packing 503 bhp at 6250 rpm and 66.2 kgm of torque at 1750 rpm.

In this day and age, when 700+ bhp hypercars are beginning to pop up everywhere, these figures may not sound like much, but you’re not going to need much more than this, unless you’ve formulated a plan to secure a prison sentence in double quick time. The powerplant is small, light and mounted behind the centre line of the front wheels, which greatly aids agility; the gearbox is placed near the rear axle, so all in, you have a rear-wheel bias, like all great sportscars.

A press of said button produces a slightly muted roar from the twin exhausts; I wish the engine had been made to sound angrier, at least from inside the cabin — heard from outside, the car produces a sharp-edged bark, which is much more satisfying, although not nearly as thrilling as the full-nuclear soundtrack that a thug like Jaguar’s F-Type R produces.

In full-nanny mode, with all settings tuned for comfort, the GT S will still blow through the 0 to 100 kph run in under 4 seconds, but why settle for comfort? Sport+ mode is the way to go, offering a you a middle ground between a modicum of sanity and balls-to-the-wall performance.

In this mode, slamming the accelerator to the floor results in the GT S blasting off its line and riding a wave of meaty torque to a 3.8-second 100 kph timing, with your head pinned to the seat the whole way.

Most opponents of turbocharging list turbo lag as one of their pet peeves, but there’s none of that going around here — the engine pulls seamlessly in a near-visceral fashion, barking and spitting all the way to its 7000 rpm redline. Throttle response is sharp and instantaneous, regardless of the drive mode you’re in, and a tap on the pedal is all that is required for the car to go galloping towards the horizon.

The 7-speed gearbox is a worthy companion to the powerplant, and doesn’t feel sluggish in the least, unlike some earlier Mercedes ‘boxes — rapidly downshifting via the steering-mounted paddle shifters causes the rev needle to leap upwards, and the engine emits all manner of wonderful crackles and pops as it does so. This is a car in which you don’t fully realise the velocities that are being achieved, however; it simply accelerates — hard, smoothly and seamlessly — and it’s only when you glance at the speedo that you’ll think ‘Oh shit, my license!’. Keep the accelerator mashed to the stop and you’ll see a top speed of 308 kph — just make sure your lawyer is on speed dial.

Pretty much any hi-po sportscar can crack 300 kph these days, however. The trick is in the car being able to hit those speeds while simultaneously offering levels of handling that won’t deposit you in the nearest available ditch. This is where the Porsche 911 has seen off all comers over the decades — it is a precision surgical instrument, designed to slice cleanly through corners with the minimum of fuss and discomfort. It now has serious competition.

I’ll bore you with just the bare minimum of technical details, to begin with. The GT S is constructed extensively of aluminium, which means it’s a light car, which is a very good thing in general. Its engine has mounts that continuously adjust for load, preventing the mass from moving around, especially during cornering. There’s a sophisticated electronic differential and robust anti-roll bars keeping things in check, too, among a host of other technological whizbangs.

As always, the end result is what matters, and the result here is sensational — a beautifully balanced, eager to please car that is sharp-edged yet forgiving. The electro-mechanical steering is really well set up, with plenty of feedback, and it weighs up as you start going faster – minute corrections result in the car doing your bidding, but without any twitchiness. This makes it a real hoot to tuck into corners, because you know exactly where the wheels are going to go.

At the famous Laguna Seca racetrack in California, with the slightly terrifying ‘corkscrew’ turn to deal with, the GT S proved an absolute master of the game. There’s so much fluidity to its handling that even a relative novice would feel at ease in it. At all times, I knew exactly what the car was telling me, allowing me to brake later and later into corners, and to get on the power quickly on the exit.

For a bit of extra fun, all I had to do was switch off the electronic safety nets and give it some extra gas — the tail would swing out, in a completely controllable way, and a little flick of the steering wheel would bring it right back in line.

The question, then, is this: is the AMG GT S the Porsche 911’s equal, at the very least? The answer is a resounding yes — you now have a genuine alternative to a 911, and you will not have to compromise on any front. The GT S looks great, goes like the proverbial from a stick, grips and handles phenomenally well, offers a fairly comfortable level of ride and is superbly put together. If you want more out of your sportscar, you’re a very picky individual indeed.