The box is sometimes more important than the driver itself. I've heard really small speakers do amazing things in Transmission Lines. Too bad the boxes tend to be massive.
More reading if anyone is interested.
The Subwoofer DIY Page v1.1 - Car Audio Subwoofer Design and Construction
Some of it may be a bit wordy, but good info nonetheless.
I may as well include a TL link for the heck of it.