I've got 4 12" subs to go behind the seat in my truck. I've got one Kicker comp SVC, 2 old ultimate, and one orion. I figured out I can get a little over 5.0 cuft of space behind there. Should that be enough? About 1.0 cuft. for each sub. (have to remember the dividers to make each sub its own box) I wondered if the kicker would perform well in that small of a box. I've got it in a 2.5 cuft. box tuned to 32 hertz and it sounds pretty wicked. Is 1.0 cuft too small? I havn't got a whole lot room to work with by the time i put 3 amps and my subs...plus all the midrange speakers i've gathered in the last 6 months!:D:D
If you want a loud daily system in a single cab fullsize truck...I would suggest going w/ 2 decent 12's in a (1)large box (as big as you can go and be comfortable driving) subs firing into your back, port low on the box firing to the passengers side.
If you build the box correctly, you should be able to get ~4.3-4.5cuft (net) w/ 40sq inches of port. (tune to ~35hz)