Mercedes-AMG is adding another open-air model to its sports car portfolio with the new AMG GT S Roadster. The GT S slots in between the GT Roadster and the more powerful GT C Roadster, with a handcrafted AMG 4.0-liter V8 biturbo delivering 515 hp and 494 lb-ft. of torque, capable of delivering its occupants from a standstill to 60 mph in just 3.7 seconds and ultimately to a top speed of 192.  The GT S Roadster brings the Mercedes-AMG product portfolio to an even dozen 12 high-performance models for street and track use.