[texanidiot25]

I want to say Pioneer had a sweet ass little setup a few years ago. It was a small box ( mail box size, maybe) that held a row of several 5-6 inch subs, in a custom box. It was engineered to produce the sound of a pair of 10s (think bose wave radio sort of killer package). Talking to a car audio friend of mine says it does live up to it's word though.

Shallow mount boxes though, dont sound as good as normal boxes. Maybe an 8 or 10 inch sub in a large, but shallow box would have enough volume inside (and ported right) to get the sound of a bigger box.

Bazoka tubes are awesome, their small, and are ported and built right, out of the box. Myself, I'll be running a 2nd-gen Escalade sub, their self enclosed 8-inch subs from Bose I wanna say. Though they tend to be hard on Amps, we shall see where it fits.