The stock stereo system in the 2002 Audi A8 Quattro was pretty amazing, but when it comes to problems it's not very user-friendly. The system includes of course, the instrument panel display with all it's bells and whistles. But the system is very more complicated. The system includes an stock bose amplifier in the trunk. And the system is also intertwined with the navigation system, And controls close to the armrest and on the steering wheel. The amp is fed power from the battery via the fuse panel. All the speaker wires feed from this amplifier. The stereo only sends signals to this amplifier. If you wish to add an aftermarket stereo and your own amplifier the best idea would be to Route speaker wires from the front via however you want, to the wires connected to this amplifier. All of the speaker wires are twisted together. They include colors- gray and yellow and gray, gray and blue and gray, and green and blue and green, and green and yellow and green, the double colored wires are the positives. You can use a double A battery to see what wires go to each speaker. Listen for speaker noise when connecting the AA battery. Seeing that the battery is located in the trunk wires from this to the amp are very easy to route to your amplifier. Best of luck! You can search the internet for wire diagrams usually the colors are similar on Volkswagen vehicles just for tip.