Carlos Lago tests Mercedes-Benz CLS63 AMG S-Model. Mercedes calls it a coupe, despite the fact that it has four doors, but what really matters is underneath the sheet metal: A 5.5-liter twin-turbo V-8 that sends 577 horsepower and 590 lb-ft of torque to all four tires. Its performance will be exceptional, but will the styling be enough to warrant the extra cost over the E-Class on which the CLS is based?