well im using the entire factory bose system with an aftermarket alpine headunit...so I can say this set up sounds better than it sounded in my old car with no factory amp and good MTX speakers. Another problem i run into is factory bose speakers run at 1 or 2 ohms, so replacing them with a regular 4 ohm speaker would mean the factory bose amp would put out only half the power. If I bypass the amp, then the factory speakers will usually fry (or overheat) most headunits because they run at 2 ohms..so i would have to replace all my speakers and bypass the amp wich I cant see being easy without a wiring diagram for the bose amp...I still cant find one lol