Its happened to my dad in his old GP, the rears literally just stopped working. We replaced them and it was fine. You could always test them with a DMM to see what Ohms they are reading. That would tell you if they are blown or not. I don't know much about the bose system and the amp. If you had any kind of spare speaker you could remove one of the non working front ones, ghetto rig a spare one and see if sound comes out. Would tell your if its the speaker or amp/wiring ect.