With a 5.5-liter V-8 that makes 24 percent more power, the ML550 replaces last year's ML500. The same engine also finds its way into Mercedes-Benz's full-size SUV as the top-dog GL550 (right). Both trucks get new looks to match the extra thrust, courtesy of AMG body styling. Of the two, the GL550's treatment is more aggressive, including fender flares, chrome trim, and a three-pointed star so big it's dwarfed only by the twenty-one-inch wheels.