I had 16" 5-spokes with runflats and changed them to 18" aftermarkets with normal tyres. I had been told that 17" give the best ride quality but compared to my previous wheels I'd have to say I made the right choice in going for the larger size. Admittedly they do take some getting used to as the handling becomes so light, but they look fab and I'd say it's well worth it :D

I'm personally like 18's but its each to their own really go for what ever you think looks best and gives you the best ride. 18's with good tyres isnt too bad just dont live near speed bumps. ;)