AMG, Mercedes-Benz’s performance division, might be running out of ideas. Its engineers spend their days creating souped up versions of regular Mercedes models; everything from SL roadster to the military-spec G-Class has gotten the AMG treatment. AMG has performed its magic on almost every Mercedes, but not the GL-Class SUV. It may be a full-size SUV, but AMG could not resist turning it into the GL63 AMG.

As with all AMG models, the biggest change is under the hood. The GL63 sports AMG’s M157 twin-turbocharged, direct-injected 5.5-liter V8 (AMG keeps the “63” in the name out of habit). It produces 550 horsepower and 560 pound-feet of torque which, Mercedes says, will get it from zero to 60 mph in 4.9 seconds, and on to an electronically limited top speed of 155 mph.

The new engine is a major improvement over the stock GL550’s, which makes 429 hp. It also makes the GL63 faster in the 0-60 sprint than a Porsche Cayenne GTS, which weighs significantly less.

Keeping that power under control is a seven-speed automatic transmission, along with standard 4Matic all-wheel drive. The transmission has three modes: “C,” for Controlled Efficiency, which starts the car in second gear and has an engine stop-start feature, “S,” for Sport, which ditches the eco-program for faster shifts, and “M,” for manual.

AMG also tuned the GL’s suspension. The SUva comes with air suspension and adaptive damping, which should preserve its cushy ride while giving it some dynamic enhancements. The ride is automatically lowered at speed for better stability. AMG also tuned the GL’s electric power steering for a sportier feel.

Stopping the madness are cross-drilled brake rotors (15.4 inches in front, 13.6 in back) and appropriately sporty red brake calipers.

In addition to those red calipers, the GL63 AMG gets a few other visual tweaks to differentiate it from lesser GL-Class models. In a classic show of sporty intent, this SUV gets a new front fascia with larger air intakes, flared fenders, and unique 21-inch wheels.

The interior also gets some changes. This is probably the only SUV with sport seats and a flat-bottomed steering wheel. There are also stainless steel pedals, and stainless steel kick plates with the AMG logo.

The 2013 GL-Class hits showrooms this September, with the GL63 AMG following in the spring of 2013. Mercedes did not give any prices, but expect the GL63 to cost more than the 2012 GL550, which was priced at $85,300.

Who will buy the GL63 AMG? There are plenty of high-performance SUVs, like the Cayenne or the upcoming Lamborghini Urus, but they are all smaller, purpose-built vehicles. Compared to them, the GL63 looks more like a school bus with a big engine.

No one will expect a school bus to beat them in a drag race, so the GL63 would make an excellent sleeper. Other than that, it shows that AMG will not be satisfied until it gets its hands on every Mercedes. Can the GLK63 AMG be far behind?