We have a chain of tire stores up here in Canuckistan that has a pretty slick webtool that lets you see if a given wheel they sell will not only work on your vehicle, but also approximately how it will look. Even allows you to approximate the colour of your X as well.

Enjoy:

http://www.tirecraft.com/pltmainpages/softwheels.asp

p.s. Sorry if this has been posted already. I haven't seen it before.