Would adding an another more powerful amp to the rear deck sub (using either a LOC or the new amps speaker level inputs) increase the bass response (louder/hit harder) and make the factory amp work better for the other speakers? Or should I replace the subwoofer driver too? I'm NOT at all interested putting an enclosure in the trunk, NOR replacing any of the other speakers either. Thanks!!!

 

I wouldn't, though some might do this. I never reccomend it because your subwoofer is made to run optimally with your amplifier (since the amp has a set of watts it juices and your speakers have a specific amount of watts its suppose ot take).

Besides, your subwoofer is a paper cone.