Don't hold your breath waiting for any help from Volvo! I've got a 2004 C70 and wanted to replace the stereo with my MP3 player. Despite the dealer saying it was fine, AFTER I paid for the car, it turns out that it is a major job to do this. Volvo said speak to the dealer. The dealer said sorry, we never put it in writting that you could.
I'm in the process now of sourcing a secondhand headunit and GPS components (probably from a scrapyard unless anyone knows where I can get them) so that I can build a PC with MP3 player, GPS, DVD & wireless network to fit the non-standard stereo bays in a C70.
The other thing I wasn't told by the dealer (Pillings in Hemel Hempstead if you need to know who to avoid) was that if I had the GT pack I wouldn't be able to have GPS! Strange that they only mention these things after they have your money isn't it?
Personally, I would never have another Volvo even if it was free!!!