thanks guys. I have a feeling my lpf, subsonic, and maybe gain are off. The gain control on the amp is kind of broken and it spins in place, so I dont really know where it is actually set at. It might be able to go higher... Some songs are much louder to the ear and move some air, while the low notes aren't as loud to the ear but move lots of air.
also, I dont think a lack of space of the truck for the sub is a problem because I've had a single 12 and single 15 in the truck and they both liked having a door or window open a lot better.