Yeah, I know Jeff since we started almost in the same time the Dynavin Hualingan competition. My X5 had DSP and when I worked with Hualingan back then there was no way the DSP protocol could be reverse engineered. I looked into other options here in NA but nobody could fake that handshake to keep the amp 'alive'. I ended up making a workaround that was also adopted by Dynavin users and Jeff as a solution.
Here is the original thread:
http://www.xoutpost.com/bmw-sav-foru...9-e53-diy.html
The Fakra cable is for NAV only. The Dynavin or any HU would have to connect the audio output to where the amp input wires are which is in the trunk... and the radio antenna.
In a few words I doubt they will ever make a DSP compatible HU.