Ok..I got my JL-C5 570x 's installed along with my JL 300/4 and audio Control LC6i (thanks langlowe for the advice on the Audio control). I found the sound quality and volume have increased a lot, but I didn't get near the bottom end I was hoping for, wishful thinking on my part right. So now, it's onto a sub, and I need to do it for under $400. I'm going to go with a JL JX250-1 amp (140$) and thats about as far as I have gotten, the audio shop is suggesting a kicker shallow sub ($100, can't remember the model number) I'm going to build my own box, but here is where it gets tricky. I don't want to get rid of my jack, and the 40 section alone is not big enough for a 10" sub enclosure, I figure I can only get about .5 cubic feet of air space. So I'm thinking that if I build it around the pillar between the two sections and stop just short of the jack it would get me closer to .9 cubic feet of air space, that should be enough for the 10" sub to breath, and my seat should still fold up. Just to confrim a few things, the sub does need to fire down right? I have allowed for a 1" air gap between the box and the truck floor, this should leave me with 5 3/4 inches inside the box. Any sugesstions for what type of sub to use, if my thinking is correct for my enclosure, and will I get enough bang for my buck? I listen to Rock and roll so I don't need to break and windows..thanks in advance