Based on your comments above, I'd suggest you go with the 18 inch wheels. Then pick a tire in a 60 or 70 series aspect ratio. This would provide you a taller sidewall for more comfort and fill the wheel wells a bit more....They are Avenue A603 rims and I'm stuck on what size I should get. On one hand, I want something that'll really fill out my wheel wells and I've seen a lot of EOC members with 20s that look good. On the other hand, I live in a rural part of Iowa and commute in every day so I was leaning towards 18s for a smoother ride both on the rough roads by our house and for the highways when I drive to work. I just don't know what size to go with.
Just my 2 cents.....