I may be incorrect, but check on the 18"... I recall reading something that, depending on the width, they may interfere. Again, if I am incorrect - I'm sorry -- I don't want to post misinformation.
I just put 17x9's on mine from a fantastic company. I don't want to list their name without the moderators' permission because I don't want to make this an advertising forum, but this guy was excellent. If you PM me I'll give you the info (Moderators, fill me in on the rules). Anyways, I've been VERY happy with the new rims and tires from this guy. If I can help let me know.
I received a message from the moderator... it's ok to disclose names on posts. I'm a noob here so just making sure I'm not breaking the rules. I save that for the road. LOL!
Anyways, for the wheels and tires -- there's a lot of competition -- but please check out www.crossroadzdirect.com. Someone else sent me there when I had a question just a few weeks ago. Outstanding service, great shipping, very personable -- and the product was excellent. Lemme know what ya think.