haven't had the honor of hearing the Bose systems the car comes with, mine was totally stripped when I bought it. But, I have read that adding an aftermarket head-unit to the current speaker setup sounds awesome. Make sure you keep the amps and everything else hooked up, the speakers need it.

Good luck w/ the re-wire.

 

jsut make sure you hook up the ampo turn on wire, usually have to cut it out of factory harness. Keep the bass down on the head unit and it sounds awsome. The way that the factory head unit was set up sent a specific level of bass to the rears and the front.