Almost every model in Mercedes-Benz's U.S. lineup is offered in an AMG-fortified high-performance version. From the C-Class to the S-Class and even the question-nobody-asked R-Class were offered in AMG trim. All except one. The GL three-row full-size SUV was the sole member of Mercedes' U.S. lineup not to receive the Affalterbach treatment. Until now. Despite our initial skepticism that such an animal existed or was in development, AMG can now officially claim full coverage of the Mercedes' U.S. product lineup.

And although the powertrain details aren't all that unexpected, largely mirroring those of its ML63 and G63 stablemates, with 550 horses and 560 lb-ft underhood, they're far from deficient or disappointing. Those figures come courtesy of AMG's now-familiar M157 5.5-liter twin-turbocharged V-8. In the GL63, as in the other hi-po SUV variants, the engine is mated exclusively with Mercedes' seven-speed multi-mode automatic transmission. The default everyday driving mode is Controlled Efficiency, which integrates an auto stop-start function, as well as activating the transmission in second gear from stops. This mode is also signified by a green ECO" light on the dashboard.

Hey, let's be real. Customers stepping up to the AMG model are more likely to care about the other two modes: Manual and Sport. Both of these performance-oriented modes disable the auto stop-start function, and sharpen throttle response. While the product literature also promises a "thrilling acoustic effect" as a bonus, we're pretty sure that's German for "sounds bad-ass." For more thrills behind the wheel, the transmission can be shifted via steering wheel-mounted paddles.

The custom configurability doesn't end with the drivetrain settings. The special performance-tuned Airmatic suspension gives the driver a choice between Comfort and Sport settings. As part of the Affalterbach suspension alchemy, the system includes specially tuned struts, an automatic self-leveling and active speed-sensitive ride-height function, active front and rear anti-roll bars, and the Active Curve System to increase high-speed stability.

Unlike its more pedestrian brethren, the GL63 is available with only a single-speed transfer case, but with low-profile 295/40R21 tires mounted on pricey twin five-spoke alloys, this sumo-sized performer is probably best relegated to the streets or the occasional trip to the chalet in Vail or Sundance.

And perform it does. Despite a weight likely well in excess of 5000 lb (official figures are not yet disclosed), Mercedes estimates the GL63 AMG can do the 0-to-60-mph sprint in just 4.9 seconds on the way to an electronically limited top speed of 155 mph.

In the AMG tradition, the interior does not skip on opulence for performance. The arms-length equipment list includes driver and front-passenger memory seat settings, multicontour seats with massage function for the front seats, three-zone climate control, AMG-embroidered floormats, special stainless steel pedals with rubber studs, Keyless-Go with a special AMG logo key fob, 360-degree camera, lane-keeping assist, a Bang & Olufsen BeoSound premium audio system, and a full-length panoramic roof, among other goodies.

Naturally, when it's time to bring down the pace from 550 horses of twin-turbo fun, the brakes are more than up to the task, with massive 15.4-inch front and 13.6-inch rear vented discs.

Exterior changes relative to regular GL models are subtle but noticeable, with quad rectangular exhaust tips embossed with the AMG logo, and V8 BITURBO badges on the front fenders, as well as the requisite AMG badge on the rear liftgate. As with all Mercedes-Benz models, customers have the option of a full badge-delete, making the GL63 nearly as inconspicuous as the GL550. So whether you're a status exhibitionist or get a thrill out of smoking unsuspecting stoplight rivals with your mysterious executive express, Mercedes has your back.

The 2013 GL450, 550, and 350 Bluetec are due at dealers in September, but if you're interested in the hot-rod GL, you'll have to wait a bit longer. The GL63 is scheduled to hit showrooms sometime in the first quarter of 2013. Pricing has not yet been announced, but considering the ML63 AMG starts at $95,865 including destination, don't be surprised to see the price of entry crest the six-figure mark. Still, for some, this level of performance in a seven-passenger full-size SUV is priceless.

Source: Mercedes-Benz