Performance speaking, is considering a 20"-21" wheel a mistake? Coming from a 996TT, the 18" proved to be a max fit for track use and overall street performance, yet many Porsche owners looking for street bling went to 19's and suffered badly with poor handling characteristics and ride quality. Is this the same situation with the M5? I would hate to sacrafice even an ounce of performance and ride for a pimp look, but those Hartge 21's look pretty nice.