Hmmmm- this make me want to ask the following question. I have a 2001 X5 4.4i with navigation and the cd changer and I want to add a subwoofer and change the speakers to some JM Lab Focal speakers, using the same size speakers that are already in the vehicle. I am sure i would also use a different amp for the speakers as well. Is this doable? Am I being realistic in my approach- don't want to change the electronics in the stereo system itself, but the speakers. LEt me know what u think