Yes, you can run H&R race springs on the e90xi. there are some pics here that you can check out :
http://www.e90post.com/forums/showthread.php?t=449209
Many people will come in saying that you're gonna need some upgraded shocks for that aggressive drop, and I'm gonna agree with that.. you can, however, use them for a while, i guess, before the ride quality gets too harsh. hope that helped!