For Edmunds’ Inside Line article: www.edmunds.com No one shops for the 510-horsepower, twin-turbocharged V12-powered Mercedes-Benz CL600 or 552-hp, twin-turbocharged W12-powered Bentley Continental GT based on price. After all, if you can afford either of these true hardtop coupes you can afford to buy them both — on the same day, using a black American Express card. These are cars for rich people. Well, not just rich, but Gordon Gekko-spec liquid. Rich enough to have their own jets. Rich …