The car: 2012 Mercedes-Benz ML63 AMG

The power: 518 horsepower and 516 pound-feet of torque coming from a 5.5-liter, twin-turbocharged V-8 routing power to all four wheels via a seven-speed automatic transmission with paddle shifters.

The photos: 2012 Mercedes-Benz ML63 AMG

The speed: 0-60 in 4.7 seconds and a 155 mph top speed

The bragging rights: Not the fastest SUV available (Porsche's Cayenne Turbo wins that distinction) but it's the most powerful. And it's possibly the best-sounding.

The price: $95,865 to start; $107,725 as tested

The details: We'll start by noting that these colossal power figures were even more colossaly-er on the model we tested because it had the $6,550 AMG Performance Package. This option group says "We laugh at your adorable 518 horsepower and 516 pound-feet of torque, but we're really in the mood for 550 horses and 560 torques." (The added power comes from increasing the turbo's boost). The package also raises the ML63's top speed to 174 mph and adds red brake calipers; a unique steering wheel; and a carbon fiber engine cover.

Our tester also swapped out the ML63's standard 20-inch rims for 21-inchers ($1,610); added piano black wood trim ($1,600) and a driver assistance package that features adaptive cruise control, blind spot monitoring and lane-keeping assist ($2,100).

All ML63 AMG's come with features that are optional on lesser ML's (like the ML350 and ML350 BlueTec we tested last fall), including a navigation system, Harmon/Kardon stereo, and an active suspension system. Other goodies include larger brakes, premium leather seats, more aggressive front and rear bumpers and quadruple tailpipes.

The drive: The best thing about this ML is the sound. Not the engine sound mind you, or road or wind noise inside the cabin; all are nigh imperceptible. It's the exhaust note that butters my toast. It's delectable. It's throaty and stout like some Detroit muscle of yore, and it will absolutely roar if you push this SUV hard enough. During shifts it kicks out a loud, extended, deep cough; think James Earl Jones trying to get your attention in a crowded room.

Also excellent was the adaptive air suspension that's designed to minimize body roll during cornering of any kind. The system does its job very well, staying compliant and comfortable over rough roads, and allows the ML63 to move with determined purpose

Things are less excellent in the steering and transmission departments, however.

The steering is a speed-sensitive electromechanical unit, used because it helps make the ML63 more efficient. But its movements are oddly light in the driver's hands and it returns too little feedback from the road. It's a little ironic that Mercedes' sport-oriented version of its ML SUV would be the one that needs to stiffen up a bit.

Meanwhile, the seven-speed automatic transmission ain't exactly quick. Even putting it into manual mode and stirring your own soup with the steering-wheel-mounted paddle shifters reveals lag.

All told, the ML63 is the muscle car to the Cayenne Turbo's sports car; straight lines in the former are just as much fun as curves in the latter. You'll get more dynamic enjoyment from the Porsche, while the Mercedes drives like a bank vault on meth.

Curb weight probably plays a role in this; though the Cayenne Turbo is down on power by as much as 10%, it's also nearly 400 pounds lighter than the ML63.

One final difference to consider? Price. A "base" ML63 starts at $95,865, while a "base" Cayenne Turbo will run you some $13,000 more.