Mercedes-Benz's CLS-Class series offers some of the most elegant lines in the category. Having been slightly tweaked for 2009, the CLS displays grace and style that inevitably makes heads turn. The CLS 550 is powered by a 382 horsepower 5.5-litre V8 engine, while at the top of the line-up is the CLS 63 AMG, a 507 horsepower bombshell fitted with a 6.2-litre V8 engine.