My impressions after wringing out the Mercedes-AMG GT 63 S, the top-of-the line iteration of the third entirely developed vehicle by Mercedes-AMG, are this: Imagine if a youthful Muhammad Ali had chosen to train purely as a track athlete, instead of as a boxer. In the much-anticipated sedan, you get the frame, power and brawn of a heavyweight, but with uncanny nimbleness and float-like-a-butterfly handling. This winning combination is equally apparent on my highway road tests, as well as on hot laps at the famed Circuit of the Americas track. The car responds like a vehicle much smaller and tighter than its relatively large footprint. To cement in the vehicle's trackworthiness, a Drift driving mode is standard in the S version, along with more conventional settings; active rear-wheel steering is also standard.

Although based on the E Class sedan's and wagon's underpinnings, but thoroughly revised for this car, the AMG's exterior goes beyond the standard sedan-onsteroids expectations. The visual cues are low, sweptback and mean. The grille and fascia, with a large front splitter, is more related to AMG's sport-car offerings, while a rear diffuser and fixed or deployable spoiler mark this vehicle as a force to be reckoned with. And what force. A 4-liter biturbo V-8 is mated with a nine-speed transmission to put out a whopping 630 horses in the S version. Blink and you'll miss the 3.1 second hyperjump from 0 to 60 mph. A good deal of this impressive performance is owing to a focus on cutting weight. A hefty percentage of aluminum and carbon fiber parts and components helps bring the GT 63 S in at about 4,500 pounds, estimated, on the scale. Burly AMG composite brakes deliver welcome stopping power.

While the four-door coupe builds on the estimable track performance of the existing two-door AMG GT sports cars, it also introduces a level of everyday functionality and drivability. Hence, we see some of the features and interior comfort cues from the relaunched S-Class sedan make their way into the cockpit to add a dose of luxurious comfort to such a speed demon. Expect signature blends of wood, leather, microsuede and carbon fiber throughout. S-Class-style multihue ambient detail lighting and even interior fragrance options are incorporated. A special Edition 1 version of the AMG GT 63, with very limited availability, ups the ante on interior élan, offering exclusive sartorial flourishes such as yellow contrast stitching and seat belts, as well as additional exterior badging, bolder air effects, and custom wheel and finish options. From $136,500, mbusa.com