The BMW radios are a pain. Each stock speaker is individually powered. And so you have to have your installer bypass it. It's pretty simple, however be careful to do clean work especially if you lease. Unfortunately, the BMW radios are an odd size, and so you can't find any aftermartker units that will fit the space. Don't worry about not have the HK, it stinks anyway. I left the HK speakers in the front. And I have a JL stealthbox (2x8") powered by an Orion amp and a 12" HK W6 sub in the trunk powered by a Mcintosh amp. Sounds beautiful. Still have the factory head unit so I didn't ruin the dash. Does the 325Ci w/o HK audio system have an amp? Planning to add a better amp. Wondering if I can use the existing wiring. I hope it has an amp so I can just replace it.