Part sedan, part coupe, and all Mercedes-Benz, the CLS is arguably the sexiest four-door ever to come from Stuttgart. It has been so successful that other European luxury automakers—namely Aston Martin and Porsche—have rushed to market with similar model offerings. As one of the first automakers to the luxury four-door performance party, Mercedes continues to rule this segment, and offers two sleek and powerful versions: The CLS550, with a 382-hp, 5.5-liter V-8, and the hot-rod CLS 63 AMG, which ups the ante with a potent 507-hp 6.2-liter V-8. Although it is largely based on the underpinnings of the previous-generation E-class, the CLS is a more involving machine, with superior steering feel and more responsive body control. For the ultimate driver’s machine, the CLS63 can be equipped with an optional performance package, which adds an AMG Airmatic sport suspension, larger front brakes, a limited-slip differential, a leather and Alcantara-wrapped AMG sport steering wheel, and, most important, a top speed bumped from 155 to 186 mph. Pros: It’s still a trendsetter. Cons: The Maserati Quattroporte is the original, the Porsche Panamera is faster, and the Aston Martin Rapide is prettier.