Hi Titch, I had Bose system fitted when I had my A4. That was in 2007 and it was a £450.00 extra to spec then (though it was worth every penny).If it is possible to retrofit, I'd hate to think what a dealer would charge - a fortune I reckon.I couldn't find a second hand Q3 with all the complete specification I wanted, and the Bose was something where I compromised - this said, I am well impressed by the quality of the standard Audi system - certainly the best in-house system of any car I have had.