Hello, If you follow the link and read the titles of the articles you will find a how to guide for installing a amp for a DSP system. The link is to a E39 forum, however I believe that the E53 and the E39 audio are basically the same. There are several articles on the subject so you will have to read through and determine the best one for your application. I have began the process to install a amplifier and subwoofer for my X5 also, however I have a Non DSP stereo so mine will be a little easier (So I am told). I hope this helps, If I find any other items I will reply with more information. Comanche