adding stock cd changer to car w/out one

my friend was wondering, i have the bose system in my car with the 12 disk cd changer and my roomie wants one now, he wants to get the bose head unit only and also get the the stock cd changer added to it and wire it into the system that is there. can i purchase a wire harness that runs the full length of the of the system, so to speak, so that i can connect the cdc to the bose head unit? also, is there a way to add a after market subwoofer and amp to the bose system? and if so, can the bose system turn the amp on and off? thanks for the help, Ritchie

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