Miro - I've no plans to take this any further at present, but If you feel included to enhance what I've done, then go ahead. The PCB I designed has the TDA1054 surface mounted, and I suppose I could have chosen to surface mount the other IC's. I don't have any solder masking/paste/reflow capability and hand soldered surface mount is a painful process.... With regard no noise and RF shielding, I have not taken any special precautions, but as I don't ever transmit on the CAN I don't do any high power/speed switching so RF emissions should be fairly low?
Tigger - the separate speaker was just the path of least resistance... on the W211 I would have to have dug out the audio gateway in the boot/trunk etc and the effort did not seem worth it.