The muscular body of this full-size Mercedes-Benz SUV, which sits on a huge set of wheels up to 22 inches, is motivated by a 362-horsepower twin-turbo V6 or a 449-horsepower twin-turbo V8, each one mated to a nine-speed automatic transmission. But don't forget the top-line AMG GLS 63 model, which increases output to 577 horsepower and uses a seven-speed AMG box. Inside the seven-passenger GLS, comfort can be enhanced with innovations like massaging front seats and a panoramic roof.