Off-topic musing...I wonder how possible it would be to interface the empeg with a satellite tuner for an aftermarket stereo. That would be a killer alternative to an empeg tuner (and about as cheap, depending on the hardware involved.) I imagine it would be a matter of decoding one of the aftermarket protocols like IPBus or AINet and then converting it to transmit over serial. I'm actually pretty surprised there aren't more projects out there to do this, as it would be useful for many projects.

EDIT: I did find this. Not sure if it's useful.
EDIT AGAIN: nope...that's their PC-Link protocol...I don't think it's used in vehicles.