AVRat,
Thanks for the advice. I figured I would update my search. This weekend I tested out a bunch of subs. I used a Dire Straits CD, the Pod Race from Phantom Menace, the tank attack scene from the end of Saving Private Ryan, and also a test disc from Infinity my father in law has that puts out frequency down to 20Hz.
1) Paradigm PDR 10. Nothing useful below 30Hz. Forget it.
2) Supercube III (the store doesn't carry II and the I is too much $). It did ok on the test disc, although volume dropped quite a bit below 25Hz. Music sounded great, but the tank scene lacked the deep rumble you want from HT.
3) Velodyne MiniVee. Accurate and loud for a tiny box, but dropped off at about 25-28Hz. Would be good if you really had a tiny room and nowhere to put a sub.
4) B&W ASW 610. Better than expected. It played louder 20-25Hz than the above subs, but did distort more when pushed using the test disc. Still, for HT you could feel the floor when the tank rolled by. List is only $650.
5) Paradigm Ultracube 10. Loved it. It handled the test without distortion and had good volume to almost 20Hz. It really impressed during the movie test. It is small and looks good. One problem..it lists for $899. Also, it has side firing passive radiators like the Supercube, so I would have to leave some room between it and my wall/couch. Still, it is small enough it would fit no problem.
So, once I get my room painted, I will probably order the SVS SB12+ and buy the Ultracube and do an in home test. The Paradigm dealer did not hesitate to offer 10% off the Ultracube, especially since I plan to buy ADP-190 surrounds from him. I feel I can talk him down to between 700-750, which would make it only marginally more that the SVS with shipping.
BTW, my system will probably be Denon 2309, Panasonic TH-50PZ85U, the NHT L5 Evolutions for L/C/R and the ADP-190s for surround. I can't wait.