Changing out the swaybars and endlinks are usually the first step in tuning AWD suspension (well technically tires first). You will greatly benefit more from having stiffer swaybars/bushings prior to doing springs/shocks.
Coming from the Subaru scene this is quite common and companies like whiteline have a very good reputation and parts selection. Was quite surprised on how many BMW parts were made as well.
http://www.whiteline.com.au/do_segue...3%2F05-10%2F11