At about twice the cost of a base ML350, the ML63 AMG requires a big outlay to enjoy its prodigious power and exclusivity. The 5.5-liter twin-turbo V-8 makes 516 hp and 550 hp with the optional Performance package. It’s quick, yet isolates driver and passengers from the sensation of speed; the handling limits arrive with little notice. Luxurious finishes befit its price, coddling occupants in leather and wood. Aside from a deliciously mean exhaust note, the ML63 performs with hushed composure.