I think most reps nowadays (off the newer wheel styles) are 20x10F & 20x11R anyway. The oem sizes for the e53 were 9.5" upfront, 10.5 rear. A 9.5" vs. 10" wide wheel wont have much effect other than looks as I assume youre going to be running the standard 275/40/20 315/35/20 tire combo. The wider wheels will give a slightly more aggressive stance......definitely can't complain about that!
Which wheels did you get?