The amps in all alero's are located on the drivers side of the trunk, up near the top, just pull back the carpeting at the top of the trunk on the drivers side and you'll see it in there, it's very tiny.. :P
Also, I second somebody figuring an easy way to hook up the stock amp to aftermarket speakers... I want mine to hit as hard as the factory ones, and they don't with just the HU powering them
