AUSTIN, Texas – When you look at the numbers, it’s clear AMG’s latest creation has a bit of a fascination with "four". First, there’s the obvious four-door configuration which leads to a cabin that comfortably seats four. The occupants will have the pleasure of the 4,0-litre twin-turbo V8 which delivers 470 kW to all four wheels through the 4Matic+ drivetrain. It also benefits from four-wheel steering and translates power to grip with some help from a set of Michelin Pilot Sport 4 S tyres. It’s not a complete maniac; at low speeds, it humbles itself to four cylinders to conserve power and lower fuel consumption. In many ways, the designers have cleverly slotted in the AMG GT63 S as a larger alternative to the menacing GT sportscar range.

AMG has made it clear it will compete with the Porsche Panamera which for years has dominated this segment with the likes of the Maserati Quattroporte and Aston Martin Rapide. Needless to say, it the Benz has its work cut out.  That’s why the appearance was crucial. Penned by renowned designer Vitalis Enns – who, coincidentally, had a hand in the original Panamera’s styling – this four-door coupé boasts aggressive and muscular proportions while maintaining a sleek silhouette to retain a sense of class. Paying attention to the finer details, it’s not hard to notice the similarities between this and the two-door GT. Broad rear flanks, slim taillamps and gaping air intakes make this an undeniable AMG from the outside. On the road, the active rear wing raises, revealing the vehicle’s sporting prowess while providing necessary downforce. The wing can remain extended with the push of a button on the centre console.

It’s the same story inside the cabin, where the new sports steering wheel features a rotary switch for the dynamic selector. A bold new centre console exchanges the usual set of buttons with numerous LCD displays. This complements the digital dashboard and infotainment system. Standard-spec bucket seats for both driver and passengers and the odd carbon-fibre trimming are a constant reminder this is a pukka performance car.

Although it looks the part, it needs to be a proper driver’s machine; a task the AMG GT executes with ease. The issue with the GT63 S, however, is that on paper it’s closer to the E63 S than the GT. Not only is it placed on the same platform, but it also possesses the same wet-sump M177 engine, nine-speed torque converter and 4Matic+ all-wheel drivetrain. AMG assures us these components and structure have been heavily revised and that it is essentially not the same car. To prove it to us, we piloted the GT63 S around the world-famous Circuit of the Americas (COTA) while attempting to keep up with five-time DTM champion Bernd Schneider at the helm of a Mercedes-AMG GT R.

COTA is infamous for its blind, sweeping corners, but its generous run-off sections do provide a bit of confidence. Regardless, I’m driving a two-tonne saloon which can rocket to 0-100 km/h in 3,2 seconds and hit a top speed of 315 km/h. With a limited-slip rear differential, variable all-wheel drive with a near-constant rear-wheel bias and the aforementioned rear-wheel steering balanced out the fear of its intimidating numbers and this world-class racetrack.

For our first run, Bernd recommended I use sport+ mode and leave the ESP in its safest setting; the result was frustrating. If the leash of the GT63 S is too tight, it numbs its personality and feels more like a hefty grand tourer. When you attempt to edge it to its limits through a corner, the ESP throttles its power output to conserve wheelspin. It also has a tendency to understeer as the distribution prevents it from overpowering the rear axle. Hints of oversteer are noticeable if you feed too much power on the exit of a sharp corner but it pulls itself back in line quickly.

Let’s take it to the extreme, then: race mode with ESP off. In this configuration, the AMG GT63 S becomes a beast reminiscent of the old days of AMG. It is unforgiving and swiftly reminds you that you are not a five-time DTM world champion. Any time you attempt to explore its limits by applying more throttle, it sends its 470 kW and 900 N.m to the rear axle and edges you in a direction you hadn’t intended. It has no desire to correct any mistake.

Thankfully, there is a middle ground. On my final stint with FIA GT3 pro Jan Seyffarth, I placed the GT63 S in race mode with the ESP in sport. I also decided to toggle the manual shift in order to control the nine-speed transmission. Here, the GT63 S works with its driver to optimise its performance. This is essential because it efficiently distributes power from the responsive throttle while preventing wheelspin and maintaining a rear-wheel bias. Oversteer and understeer are seemingly absent as you are more aware of where the limits lie. Managing the nine speeds with the wheel-mounted paddles is easier thanks to the flashing notification on the digital dash and creates a more rewarding experience.

After stepping out after my final stint around COTA, I was filled with admiration for AMG’s family bruiser. It’s a no-nonsense sedan which can hold its own on the track and on a family vacation … much like an E63 S, in fact. It doesn’t take you long to realise it ticks the same boxes as the E. It’s true the GT63 S boasts an additional 20 kW and is faster to 100 km/h by 0,2 seconds yet, from behind the wheel, the only notable difference is its overall stability and the speed at which it can change direction thanks to the rear-axle steering and noticeably short lock-to-lock wheel rotation. Additionally, despite its stiffer underpinnings, based on this first impression it provides an improved quality of ride over the E63 S.

Whether that means the GT63 S is a tad too soft is another matter. I had hoped for the brash, unfiltered experience I’ve come to appreciate in the AMG GT variants. Buyers, however, may just like how the four-door straddles both the performance and comfort parameters.