Mercedes-Benz stunned audiences at the 2013 Frankfurt Auto Show with its Concept S-Class Coupe, and soon we’ll being seeing its production cousin, which its designers promise will retain close to 90 percent of the sultry concept’s lines. The new S-Class Coupe, the replacement for the CL-Class, is expected to debut early next year, most likely at the 2014 Geneva Motor Show in March, and soon after we’ll see the debut of its high-performance AMG variant.

This AMG variant, which we expect to be called the S63 AMG Coupe, is the focus of our latest spy video. A prototype was recently spotted testing at Germany’s Nürburgring and provides a taste of the performance the big bruiser will offer. We can tell it’s an AMG variant due to its enlarged air intakes, front splitter, uprated brakes, quad-exhaust tips, and AMG-style alloy wheels. The prototype also sounds very similar to the recently launched 2014 S63 AMG sedan.

That means the car is likely packing a direct-injected and twin-turbocharged 5.5-liter V-8 tuned to deliver 577 horsepower and 664 pound-feet of torque. In the S63 AMG sedan, this engine, mated to a seven-speed AMG SPEEDSHIFT automatic transmission, delivers a 0-60 mph time of just 3.9 seconds. We expect the S63 AMG Coupe’s time to be just as quick or perhaps a little quicker still.

The key to the car’s performance will be standard 4MATIC all-wheel drive, at least here in the U.S. market. AMG’s version of 4MATIC features a 33-67 front-rear torque split, offering the rear-biased feel we all love but with the added traction of all-wheel-drive when roads get slippery.

A V-12-powered S65 AMG Coupe is also likely to be in the works and should share a 621-horsepower twin-turbocharged V-12 with the recently revealed S65 AMG sedan and the SL65 AMG convertible.

The interior of both cars should match that of the S63 AMG sedan. This means AMG sports seats, an embossed AMG logo on the center armrest and an AMG sports steering wheel.

Key rivals will include the Aston Martin DB9, Bentley Continental GT range and Maserati GranTurismo.

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