My car is a 2003 Mitsubishi Galant with 4 Digital Designs 1010 subwoofers (10" 600rms 4ohm SVC each) in a custom ported box, powered by a Concept amplifier that pushes 1000rms@4 Ohms. I have 0 gauge wiring running to the amplifier, I never drop below 12 volts. What is the best bang for my buck to get it louder? Would the big 3 make any difference? And is there any kind of amp that I could get that would push them better with the stock electrical? I'm not sure if the Concept puts out rated. The subs are currently wired @ 4Ohm but I can wire them down to 1, but I don't want to spend a bunch on an amp if it won't make it much louder. Thanks!
EDIT: One more thing, I got a Planet Audio crossover for free, it has a line driver built in, is there any reason i'd want to use this?