[Rumnarv]

Make sure you still have the origional BOSE speakers, if not you will need them. Aftermarket speakers are 4 ohm where BOSE speakers are 2 ohm.. The aftermarket speakers will be the same thing as using an amp with half the power. With the bose you need all the power you can get.

 

[Rumnarv]

can i put an aftermarket amp in the premium system?

and if so what kind of mp would i need? how many watts, and all that stuff

http://www.tweeter.com/product/index.jsp?productId=2157395&cp=1124542

would that work?

It would work, but you would need a wiring diagram to locate the correct wires. The signal going into the BOSE amp should be at a pre amp level. The only thing I would worry about is the fact that the wires are probably not shielded, so you may get some unwanted noise.

It would probably just be easier to get a comple aftermarket system.