Hi, all, a newbie here. I am getting a new '06 CTS with the 3.6, a hole in the roof, auto trans and lux package. My question is this: What are the differences, besides the obvious, between the 18" Wheel Performance Package vs. the 17" wheel Sport Package? I realize things like 18" wheels vs. 17" wheels, etc. My main questions are related to items like the Performance Brakes and the Suspension. Since this will mainly be my wife's car, major mods are probably out of the picture here. I have searched and have not been able to find anything on this topic. All help is appreciated.