• We decided to get acquainted with the Cadillac V-Series cars, factory-tuned performance versions of the CTS (the entry-level model), the STS (the Euro-style sport-luxury sedan), and the XLR (the convertible with the retractable hardtop), to see if GM's luxury division has the goods to take on BMW M and Mercedes AMG cars, not to mention tweaked sets of wheels wearing Audi RS and Jaguar R badges. What we discovered during a week of driving all over Southern California might surprise you. It sure surprised us.