This post probably got lost in all the ungoodlyment, but I'm interested in ths too. Here's another question...
1. A volume knob is just a fancy resistor, right?
2. A subwoofer's loudness (without going into details) is controled by the volume of your stereo, right?
3. SO, if you installed a variable resistor between your inputs and subwoofer, could you control the loudness with that?