This is not meant to be offensive but the real reason your pulling so many amps is cause your amp are cheap. Sony and pioneer aren't the best out there. If you got Rf'* or MTX, your system would play twice as loud and cleaner with less wattage. The amps you have are rated sucking alot of power and the better amps are rated using around 12.3 volts.
I would also changed the sub set up . If they are not properly phased out , you may just be canceling you sound out.
Sell you amps on ebay and get MTX, If it'* not louder. then it'* your subz. They suck too. You should get sealed box for your trunk. A band pass is tooooooooo big for your trunk. It won't breath properly.
Youd be surprised how many carz I shut down with just 1 12"