Up for sell is the Harness Add-A-Sub by Technic for E60 model (None logic 7) HIFI stereo system (option 676 or HK 674). This harness come in handy for some one just want to add a sub woofer to an existing HiFi system without cutting/splice the original wire. This is plug-in the original Amp connector and the module will convert speakers high level signals to low level signal (RCA) to your sub amplifier. I had this install to my 2010 BMW 535i and just sold the car last few weeks.
Asking for $55 Shipped. Moved to F10 no longer need this signal converting modue/harness. PM me if you're interested