I believe I saw somebody on Audigon who had several, brand new, Ifinity HPS1000 subs for sale. 18-120Hz, 1000 Watts, 15" downfiring woofer and two 15" passive radiators. Allows for control of Phase, gain, crossover, inputs, and EQ. This unit was ahead of its time and I have never heard a crisper, cleaner, sub. At any price IMO
You should contact Kyle at www.acoustic-visions.com or Brian Bunge at Link Removed with your budget and bass goals. They can custom build you a sub to match your needs. Both of them frequent this forum. I've never had anything done through them but their prices are quite reasonable.
Thanks to everyone for the input and suggestions. As with any home theater purchase, you inevitably exceed your budget, although it seems that I should be able to get what I'm looking for from Hsu or SVS (or perhaps Rutledge or Acoustic Visions?) for around $500 or perhaps just a little more than $500. I'll be replacing a JBL PSW-D110 (which still works, but I've recently started upgrading my system and, well, you all know how that goes).
My Hsu TN1220 was a bought for a little over $400; however, since it is a passive sub, I had to buy an amplifier, and to take advantage of the lowest response of the unit, I had to purchase a Hsu Bass Optimizer ($100, it really works!).
Factoring in the cost of amplification, it is almost impossible to get a flat response down to 20 Hz for under $500, unless you stumble upon a very good deal on a used setup.
It is very difficult but I think it can be done without going used. The reason I recommended the custom built subs above is becuase I recently found out Kyle charged a guy(from the Klipsch forum), $500 for sub a which was comprised of a Styke AV-15, 2 18" passive radiators, and I think it had an oak finish. I don't know if that's normal pricing or if they had a special deal going on but it's one heck of a sub for $500.
Now I know that doesn't take in the cost of amplification but if you take a less expensive woofer than the AV-15(like the Tempest), go with ports instead of passive radiators(this really reduces the cost), and a black paint finish instead of veneer then this would *probably* allow for a plate amp within the $500 budget.
No way to know for sure unless Paul contacts them. Besides this or used, the best bet is DIY. With a $500 DIY budget, solid high output at 20hz(and below) is a piece of cake.
Can you do an infinite baffle sub? For more info on IB subs go to "Cult of the Infinitely Baffled" http://f20.parsimony.net/forum36475/index.htm . Two 15" Tempests drivers from Adire $300, plate amp from partsexpress approx $100, and the remaining parts- MDF or plywood, 12ga. wire, etc. with the remaining $100. Will beat any none IB sub under several times the price.
Call Kyle at Acoustic-Visions.com. For your budget, you can get more bang for your buck than the three choices that you have listed. If you don't have the tools to do a DIY sub, he can sell you a complete kit that you can put together. Tell him what your goals are, he won't steer you wrong.