There is an article in the current Bimmer magazine which details a rebuild of the front suspension. They also install Bilstein front struts. Instead of using aftermarket springs, they simply cut a coil off the front spring--lowering the car 1" and increasing the spring rate by 20%; about the same as most aftermarket street/lowering springs. While most people will chastize you for cutting springs it is often not a bad solution when done properly. Great way to save a couple of bucks too.