I have new information from my car dealer. The Bose system in the 8 is the next generation of the Mazda 6 system.

For the Mazda 6 there's Add-on modules: Tape is ~ €150.- (=~150$) ant MD is ~ €500.- (=~500$) :-(

For Europe, the 6cd's changer in dash is standart in High-Power version. I Dont know for us...