It's actually a quad 18" sealed subwoofer. Two Carvin 1800w amps power it. It is a very cozy, comfortable room. I've spent wayy too much time in there since I built it. At least my wife knows where to find me.
Here's some of the construction pics:





Back of the room:

Lobby:


I took alot of work but I am completely in love with the results. HD movies are stunningly good, and the audio is mind-blowing.
For equipment, I currently have:
Epson Pro Cinema 1080p
Integra DTR 8.8 Receiver
Integra DHS 8.8 HD-DVD
XBox 360
Sci Atlanta HD-DVR cable box
Monster Power surge
PSB CH-80 mains (3)
PSB CW-383 w/ acoustic chambers for rears and side surrounds (4)
Next step is the acoustic treatments, then a
real calibration and eq.
Enjoy!