Bose speaker problem...

Hello all... have a slight problem. I have a stock stereo system AC Delco with Bose speakers that came with my 2004 Yukon. The Radio turns on I can access the volume control and also change radio stations. Although there isn't any sound whatsoever! I have checked all of the fuses which I believed to be the first step and have no idea how to go from there... I am positive I haven't blown all four speakers... am I missing a fuse somewhere other than the fuse box under the hood or in the cab or is the Radio shot? Any and all help would surely be appreciated. As you know I am not electrically gifted but understand some. Guess if it doesnt start working its on to buy a new car stereo..lol Which isn't entriely a bad idea unless I can get this one working again for the time being.

check the stereo controls for the back seat, sometimes if it is turned on the speakers wont work