Hey JoeHK,
Unless you go for something extreme in 18", they won't rub.
I have 18x8 rims (vs std 17x7) with an ET of 45mm (vs std 48) and 225/35's on it, no rubbing and pretty 'grippy' and firm. Ride height remains as stock, balance remains unchanged and the wheel wells are symetrically filled. They do cost me well over 1-1.5L of Euro98 per 100km
but as L'Oreal says ... they're worth it !