Ellen:

I built mine from ground up based on “Shiva White Paper” in their website (adireaudio.com). It is down firing configuration on 5 cu ft (internal volume) enclosure with one 15 inch passive radiator. Interior surface is lined with acoustic sponge (looks like egg crate) and also it is stuffed with 4 pounds of polyfill. According to “Shiva White Paper” it is tuned to 17.3 Hz. That’s low enough for just about any music or movie. The sound? Tight, clean, sweet, powerful and ... etc, you name it. I couldn’t ask for more from a $450 subwoofer. A store bought subwoofer at this level will run you at least $1,200. There’s a big benefit of doing it yourself. I’m surprised not to hear more gunslingers going for Adire Audio.

You can order enclosures and amps from here.
http://www.acoustic-visions.com/~acoustic/products/subwoofers/enclosures/

Good luck and please let the gunslingers know how it went.