well that's the thing at first they aren't going to have much airspace, i have a chevy ex-cab silverado and they will be put under the back seat, well i will custom build a ported box, the box will be the seat basecally, these trucks arent really good for boxes cause of the humps in the floor, but i have to keep the back seat for the kids, lol well i plan on getting a tahoe eventually but not anytime soon, then i will have plenty of room in the back, i just wanted to get the subs that ahead of time, the box with 4 15s would be really tight, cause the demensions i am going to use is 55 inch long, 21 inches high, and the depth is 16, but i may use 18 inch depth, and the cvrs are 8.5 inch mounting depth, cause they would have to back up to each other in the box 2 facing foward and 2 facing back, port back. i just want a loud setup, well the port i plan on is 32 hz? thanks