Ah yes, sorry about that. It's a 2000 E class.
The headunit has indeed a fiber option connection for the CD changer. It has - like yours - only power and the optical input (which isn't used on mine since I don't have the changer). The controls to the steering wheel and display go over 2 wires only. Unfortunately, the illumination, ign sense and phone mute go over these same 2 wires. So this means that if I want to install the empeg, that I would need to run new wires for illumination and ign sense. I was hoping I could at least find an adapter for those. I don't mind about the display and the steering wheel controls really. I just don't want to start running new wires.
What bugs me too is that the Bose amp uses to speaker outputs of the headunit as input (hi-level) and not a pre-out. This means that I cannot connect the empeg to the Bose amp either. It needs hi-level. So if I want to keep the Bose, I would need to install an amp between empeg and Bose amp ... Sjees ...
Of course, I could dump the Bose but than I loose the subwoofer