ok, im buying either a s10 ext cab or a ranger ext cab(both have about same spaceing in back and both have fold up pilot chairs in back.) i was wonder how many cubic feet i can get out of one, because i was thinking of trying to fit a 12 or possibly if i could fit a 15 xxx, mayeb some other but i wanted to know how many cubic feet i could get, and i did search but all i found was on reg cab trucks. Also, how should i face the box, upward firing, angle back towards the back window, or if i could make a downfiring? thanks alot. o and im doing thinf because im selling my monte carlo(had tons of room) adn switching to a truck, and i still want a killer system.