u need to check the off set dude, most acs (well all the orig and non copy ones) iv seen in the uk will not fit a 3 series as designed for a 5.....But like i said thats only what iv seen andits not unusual for me to be wrong!!
As for the size the ride quality will be 5hit but they will fit..as for width check the search function theres been loadsa threads on wheel size..i run 18's and the fronts rub (8") if i turn full lock but the rears are fine (8.5")..Think u'd have probs with anything much wider unless u roll the arches