Confused over wheel offsets
 

Hi all merry xmas.
I have beem looking for some 18in wheels to put on my hawk sti but dont know what to do about offsets.
I am currently looking at these
18x8 114.3 pcd et45

https://cimg5.ibsrv.net/gimg/www.sco...8a37542bc9.jpg
Will they fit a hawk sti on prodrive springs and will putting et45 have any effect on handling / steering. I dont want to spend that kind of money to findout my car drives like poo.
My other option in to just chuck a set of prodrive gt1s on it .
Thanks jon