If your car came with the Bose system from the factory, you need to buy a little adapter due to the way bose runs it's amplifiers. Basically you can't run the Aftermarket Head Unit amp, on top of the Bose Amp, so the little adapter deletes the Bose Amp and allows your car to be powered by the single Head Unit amp.
In Lamens terms... buy the adapter, you will have sound. It's a pain in the ***, considering you have to spend like 40-50 bucks to get it... but I'm pretty sure it's the only thing you can do if your car came with BOSE. http://www.logjamelectronics.com/piehrcgm21.html