FIRST DRIVE: MERCEDES-AMG C63 S COUPE

Price: $70,000 (est.) 

Powertrain: 4.0-liter biturbo V-8,  469 hp, 479  lb-ft; rwd, 7-speed automatic 

Weight: 3770 lb

0–62 mph: 3.9 sec

Top speed: 155 mph

On sale: Summer 2016 

We savored every mile and every snarling backfire in the old Mercedes-AMG C63 Coupe, but here's the brutal truth about a brutal car: It was compromised. The outgoing two-door was a hastily contrived, late addition to the previous-generation C-class lineup, and suffered for it. Can you imagine another carmaker entertaining the idea of charging more than 60 grand for a coupe with sedan-style, framed-door glass? The old C63 Coupe also performed just like a C63 sedan, which wasn't quite enough to go head-to-head against purebred two-door sports cars. Yes, it had that unforgettable exhaust note, and it was always up for some sideways fun, but it never felt as well conceived as the best competitors.

With the new C63 Coupe, AMG gets serious. Visually, technically, and dynamically, the Coupe is distinct from its four-door brother—and is superior by almost every measure.

It's also, shall we say, girthier. The C63 coupe shares only its doors, roof, and trunk lid with the standard coupe and is about an inch wider than the AMG sedan. The track is 1.8 inches wider than the AMG sedan in the rear and an inch wider in front, partly due to meatier tires. The rear suspension is mounted to the body with stiffer bushings. Its booty is half Kardashian, half ur-Quattro.

That big booty can really move. The C63 Coupe has the kind of traction a C63 sedan driver wouldn't believe—at least until the tires get too hot. You feel the rear tires edging out of line slightly, and with stability in sport or completely off, you'll still have to contain—or revel in—the oversteer. But compared with the sedan, it feels more precise and more neutrally balanced. It wants you to have fun, but not to lose precious tenths for the sake of it. That makes the C63 Coupe the best of both worlds and better controlled than any 3800-lb car has a right to be. Don't worry: Lurid, tire-smoking powerslides are still on speed dial. 

Plenty of the major hardware does, of course, come from the four-door. That means the sedan's twin-turbo, 4.0-liter engine replaces AMG's boisterous, naturally aspirated 6.2-liter V-8. It makes 469 hp in the regular C63 or 503 hp in the C63 S, same as the sedan. It certainly has the muscle, hustling from 0 to 62 mph in 3.9 seconds, according to AMG. If you want it to make anything like the noises of the old 6.2-liter, though, you'll need the optional sport exhaust. Otherwise, it's rather muted.

Mercedes USA reckons almost every buyer will reconcile himself with the likely $10k premium and sign up for the C63 S model. It comes with larger front brake rotors, dynamic engine mounts, and an electronically controlled limited-slip differential. It also has a fifth setting, Race, on the rotary dial that selects drive modes.

The C63 still isn't a true sports car. The steering feels quicker and more precise than before but still doesn't communicate as well as we'd like. The turbo engine is plenty responsive, but the seven-speed automatic transmission lacks the instant response of the BMW M4's dual-clutch transmission. And there's no getting around the fact that this is a big car, bigger in every dimension than an M4, and a huge 337 lb heavier.

That said, the C63 makes an M4 feel about as refined as a Philadelphia Eagles fan. Hopping onto the freeway at the base of a challenging, rock-lined road, we flick the Dynamic Select control to Comfort and our rowdy ride settles into a cosseting cruise. A disappointing murmur of wind noise spoils the solitude, but otherwise, this feels every bit like a luxury car. The richly detailed interior reinforces that feeling. Other brands' coupes major on performance, some on luxury. But none melds the two as successfully as the Mercedes-AMG C63 Coupe, a genuine 24/7 supercar.