By chance I had a ride this w/e in our neighbour's new A3 (is that the same as an S3?)which does have the enhanced Bose system they offer installed as an option. I have to confess I was rather impressed by the sound quality; if nothing else the speakers are impressive. I honestly don't know if the head unit has a built-in amp or if it is seperate, so I can't comment on how you would add an empeg to the system - but I certainly would look at buying the option installed and retaining the speaker system.