Babe, just stick with the 17's
I had 17's till they got nicked and to be honest i didn't think there was anything wrong with the handling untill i wacked on my track wheels which are 14's on tractor tyres. Damn i can now take corners at double the speed, although i do get a bit of slide as they are about as wide as a bycicle tyre. Even so, as soon as i can afford a set i am going straight back to 17's
Although i quite liked the rally style look that the small wheels and larger tyres gave the car, i think that a big set of rims just finishes the car off a ttreat. I would go for 18's as some people on here have, but i have been told that with the R's power when you put the foot down the car would be all over the place, so i guess 17's are as big as you can go, if you participate in a bit of exciting driving.