I've had 17inch wheels on both my RS/SC/Carrera-flared car (R.I.P.) and my RSR-flared car. I think Fuchs look the best on a 911, but that's just my opinion. My 17's are 2-piece wheels made with Fuchs centers.
Wider version is on top, skinnier version down below:
And a more-flattering look at the wider car:
