Happy: I have DSP too. I've followed these types of threads with curiosity. I added the OE Aux input to my system early on, maybe in 2004. First I ran it so the wire went through to the cupholder. Removing the middle console to do that was a pain.

Now I have the Aux input running to the glovebox. I had an old adapter, from my e30 325i, to convert the flashlight charger to a 12V cigarette lighter port (switched!). I bought a Kensington Bluetooth adapter in 2006 to plug in there. I've been using that since. The sound quality is decent, not great. I'm sure there are better performing similar 12V adapters now. One nice feature is it came with a remote that wraps nicely around the gear shift knob.

Last year, I added a 12V splitter adapter in the glovebox. I added front and rear wireless license plate cameras. Their display power plug is in the other side of the 12V splitter.