The best combo I've found is the Eibach kit from bavauto.com for springs and the sachs shocks/struts from bmaparts/bavauto. They offer a nice smooth stable ride without being overly stiff. Also, you don't need to modify anything with OE wheels. If you want cheaper shocks, you can go with KYB GR-2 shocks. They work fine for a bit less. They are a little stiffer than the sachs, but they both last a long time. So, sachs and eibach are my vote for a hassle free lowering.