Bose retrofit
 

I have almost all options on my 02' A8 and one of the missing options is the Bose audio system. I've had it in my previous A8 and i'm missing it most of everything ever in a car!
I know that the retrofit IS possible but I want to know if I have to install all new cables or do I just connect new speakers and the amp with the headunit?

You have to replace the whole harness, from the boot up to the head unit, as the Bose system has larger speaker wires and low-level outputs for the amp which the standard system doesn't have. All the antenna cables for nav, radio, tv etc are also in the same harness.

Seats, carpets, rear shelf and centre console out to get to it all, but its easier to do that than to try and pick apart the harness.

I think IT did it a long while ago and documented it too.
Pretty big job as MJ has said.

By modern standards it’s just an average system anyway. You’re better off getting an upgraded headunit and speakers.