I just recently bought a 2400 rockford amp...which equalates into around 900rms @ 4 Ohms bridged.... 200rms x 2 at 4 ohms or 400rms x 2 at 2 ohms... Right now i just have an old sub rockford he2..which is around 400rms... I previously had two with an 1800 amp.. With this one i can turn it up...and when i turn on the bass boost you can tell the sub just cant push out any more... Rockford sound benched them (Whatever you wish to call it) at something like 450rms per channel.. Do you think it would be better to get 2 subs and run 2 channels...or just one and get a 4 ohm sub or dual 2 ohm sub. And I am much for quality than really Boom.. But with 900rms it should have plenty of boom

 

I would just get one sub that can handle the power you need. I am running 1200 RMS to a 15" L7 and it pounds pretty good. You really don't need 2 subs in a Cobalt since it will consume most of your trunk space and is not really needed.