could be wrong here lad and i'm sure someone with more knowledge may correct me , Doubt the ride height will alter maybe a few mm, but the sti spring might give you better handling , i'd imagine if you want the car to sit lower a set of whiteline springs might be better suited plus the handling should be improved 2 ,
as far as i know there is a noticeable difference bud, mabye 20-30mm, my old type r was on standard suspension and was a good bit lower than my old wrx, both classics tho, but both with standard shocks and springs, hope this helps