I upgraded my system by adding a 10" sub (JLAudio),placed where the stock subs were. Additonally, I added a Precision Power PPI PC 660 amp installed where the tire jack was (behind the spare tire). Replaced the speakers with MBQuart DSD front and back. I did not get the BMW premium upgrade (listened to it, was not impressed). I kept the stock radio and the sound in my X5 is the bomb!!!!