If you ask me 18s are perfect. Saleen allways knows whats up 17s on fox, 18s on 94-98s, and 20s on 05s.
I think 18s look great, I would personally never go smaller on my car, I would love to actually have 19s lol but its hard to find nice ones.
Anyways Im really happy with mine. You will notice your braking will not be that great, chrome is the worst. I have chrome 18" and my braking isnt that bad, but I think im going to upgrade to the larger brakes down the road (cobra)