We've said it in print. We've said it to Mercedes-Benz. We've told our friends. We've even admitted it to our therapist: The Mercedes-Benz R-Class has a weight problem. Tipping the scales (tipping them over, actually) at around two and a half tons, the R has no natural enemies in the automotive arena — it looks like a Sumo station wagon, but any BMW or Audi luxury wagon you'd try to put it up against would get lost in its massive shadow. And while the all-wheel-drive R-Class is built alongside the M-Class and G-Class SUVs in Alabama, nothing about it makes you want to even consider putting dirt under its wheels (a fantasy you might entertain with a Porsche Cayenne).

Rest assured: If you want to drive an exclusive Mercedes to your bridge club or an estate sale, the R-Class will give you that feeling of "Am I alone here?" But for those who really want to shave the extreme tip off the exclusivity iceberg, starting in September you can special order — that's right, Special Order — a 2007 Mercedes-Benz R63 AMG 4Matic for $87,400 from your local M-B dealer.

A matter of mass
As alluded to earlier, the primary challenge for AMG was the dead body of weight represented by an R-Class. Seriously, a 5000-plus-pound automobile is a lot of work. Driving our long-term R500 (302-horsepower V8), we can feel engine muscles being strained under acceleration, and we can almost hear the front brake rotors wailing, "Oh, God, not again!" as we ask them to put a stop to the R-Class' mass in motion.

Clearly, the first challenge AMG threw itself up against was in making the effort of turning an R into an AMG seem effortless. Fortunately, the super-tuners from Affalterbach possess an awesome set of tools.

Bring on the best, Part 1
"Many horses make light work" as the saying goes, or at least it ought to. And the R63's 6208cc aluminum V8 — no turbos, no superchargers, just 32 valves breathing sweet, natural air — makes moving the R seem like very light work. From the crank to the cams to the cylinder-bore coating, AMG triple-sweated every detail in building the 6.2-liter eight to a power output of 507 hp at 6800 rpm. The 465 pound-feet of torque peaks at 5200 rpm, but the engine begins to play near that lofty summit much earlier in the rev range, resulting in a sublime band of power.

Connected to M-B's seven-speed automatic transmission — offering a driver-selectable choice of Sport, Comfort and Manual shift programs and steering-wheel-mounted buttons for "manual" shifts — the engine sounds like heaven and moves the R63 out with style. AMG didn't touch any of the ratios from the standard R-Class gearbox (the ratios are great for this engine), but it did add a taller final drive and the magic of Speedshift. AMG Speedshift programming should be the standard of the industry, pulling off quick, clean upshifts and downshifts without a hint of indecision.

At the aft end of the fuel-burning process, an AMG sports exhaust with ceramic catalytic converters and bigger pipes improves both the fumes and the flow. Autobahn bred, 110-120 mph is where this car would ask that you cruise all day long. And Mercedes' claim of 4.6 seconds to 60 doesn't seem at all overly optimistic.

Bring on the best, Part 2
The R63 AMG rides on a newly developed AMG sports suspension that enhances the front double-wishbone, rear multilink Airmatic suspension. AMG stiffened the suspension and shock rates so well that the R63 now feels like it offers zero body roll. None. Combined with the full-time all-wheel-drive 4Matic system, the R63 delivers a nearly unshakable footprint in the corners. Like every other R-Class, the AMG R wants to push (as you'd expect), but you never get the feeling that the R63's heavyweight cornering forces are trying to rip control right out of your hands.

Even in Comfort mode, the adjustable suspension exhibits a fairly high degree of firmitude, but the R63's weight works in its favor here, loading up the suspension and offering controlled comfort over long distances. In Sport mode (and at speeds above 43.5 mph), the body hunkers down automatically by about half an inch.

Getting an R-Class to move is a challenge, but getting one to stop is a labor worthy of Hercules. AMG has mastered the Art of the Stop with the R63, using Texas-big brake rotors (15.4-inch diameter in front, 14.4 inches at the rear), drilled and vented. Under hard braking at high speeds — the higher, the better — the driver is treated to that amazing AMG feeling of an absolute stop, as if the R63 is being sucked into the ground. Pedal feel ranks right between the firmness of a BMW M car and the uncommitted softness of Audi's S sedans.

There wasn't much feel to the rack-and-pinion steering, despite snappy turn-in from the optional-in-Europe 21-inch AMG alloy wheels (U.S. models get 20-inch versions of the same wheel). This contrast of low feel and sharp turn-in made it irritatingly easy to over-input the R63 into turns, often requiring a slight steering correction to return it to the cornering line you had in mind.

Into the great wide open
Imagine a football field upholstered in leather, and you've pretty much got the idea of an R-Class interior. To this roomy galaxy, add an AMG sports steering wheel with gearshift buttons, sport seats with special AMG logos and trimming, an AMG instrument cluster, rubber-studded stainless-steel pedals and AMG door sill plates, and you've got yourself an R63 interior.

Somewhere between genial and genius
Curbside, you'll be able to spot a Mercedes-Benz R63 AMG by the aforementioned five-spoke AMG wheels, revised front and rear bodywork with tinted taillights, the "6.3 AMG" badges on the front quarter panels and, exquisitely, the quad oval tailpipes poking out from beneath the rear bumper.

In many ways, AMG accepted its biggest challenge in doing the R63. Teaching a beast like the R-Class to dance, making such an abundantly heavy car seem light on its feet, is really quite a stunt. But they pulled it off. Next up for AMG: world peace, time travel and figuring out women.