actually I think those will fit...mine are 18x9 and I have no clearance problems. You wouldnt be able to rotate with the wider rears. There was another guy on here that was running the wider rims on the back because he liked the look since the GP has a narrower rear track than the front. He liked the "evened up" look the wider wheels gave. $300 would be hard to walk away from.
My Santa Cruz rims came yesterday but it has been monsooning here the past two days. I hope I can dry fit one this afternoon when I get home. I have my resrvations about these tho...not exactly what I was hoping for. I may just have to scrap the white letter thing altogether.
Good luck on whatever you decide.