I'm currently looking for a 03/04 B6 S4 - hopefully with DVD SatNav. But they seem to be fairly rare in my price range (22K). The other option is to retrofit one, and I have a couple of question that hopefully someone can answer... 1. What are the differences between the OEM satnav versions (RSN-D, RSN-E, MMI) 2. What does the B6 S4 come with as standard (most seem to of had the BOSE upggrade) 3. Does the head unit fitted affect how difficult it is to retrofit a new unit. 4. How much is it likely to cost, I see you can get a RSN-E unit from ebay for about £400. Is it a case if just swapping the units over or does it require a professional install? 5. What about the bluetooth and TV options. Is it worth doing these at the same time? Any help much appreciated.