hi everyone newbie with a question

[gabyX5]

ive been a member for a while but ive never had the chance to post because i just got my X5. My question is i just purchased a set of replica style 168 20's, 10 1/2 rears, & 9.0 for the front. I was supposed to get 9 1/2 for the fronts. But the guy at the store said that they only have 9.0's. What kind of the tires would i have to use to fit the 9.0's or will the 9.0's affect the driving of my X5 with 10 1/2 in the back? And will that half inch make any difference with the 20's? Ill be posting pictures of it before & after. Any help with be greatly appreciated. I have 2 days to decide if im going to keep it or the store will refund my money. Thanks