AZNz28

Heya guys, I drive a stock green z28 and wanna dress it up first. I was lookin at tirerack.com and thought the ssr rims were really nice. I don't mind payin that much, and they're pretty light. However, I would rather have the Competitions, but they only come in 18x9.5. Are 18s fine for my car, will the car bottom out? or should I buy the gt1s in 17. Here's a pic of the GT1:
(http://www.cardomain.com/member_page...rolet%20Camaro)

Here is a link to the tirerack garage thingie:
http://www.tirerack.com/upgrade_gara...&autoYear=1998

BTW, does anyone have SSRs on their rides? Thanx for the help dudes.