Interesting history of low frequency nutrition...
I have been looking into this stuff for awhile now, not having been interested in the past too much in subs. When I built these two LARGE 50 inch bass transmission lines of Greg Monfort's design, I got a whole new lease on bass life. Now hooked on wide range drivers, horns and open baffles, they become a necessity.
The idea of sealed boxes is a given. With wide rangers speed becomes paramount in importance, especially with a ClariT amp, because the thing is soo damn "fast." Attack transients are blinding!!
For a smaller room like mine and presumably like Richard's, I would SERIOUSLY look at the Adire Audio Koda 8.
www.adireaudio.com these are the guys with the XBL motor tech., and it keeps up with about any 10, and alot of 12 inch drivers apparently. You could mount these in the Parts Express .75ft^3 finished cabinet, use two 150 watt plate amps, I believe they have one with 4th Order XO., and put them behind the Omegas, along the wall. The PE finished cabinets are really beautifully finished products, the photos do them no justice. I have the cherry veneer. They also have interchangeable baffles, making the cabinets re-useable for other projects/speakers. If I had a bigger place, my plan would be to use four Kodas in the .75ft^3, sprinkled along the back wall, to ameliorate room modes. These are like slightly smaller Shiva subs. Smaller cone means less mass, means faster transients. This driver will make 35Hz in a .5ft^3 sealed cabinet.
If you look at the Koda 8, you begin to see that it is unique. It is from the same people who give you the Shiva sub, which is pretty much a standard in excellent high value subs. You could whip up TWO of these things for about $400. How's that for ValueKing Audio??
To start with ONE sub, which may do it for you, I would also look at the very nice floor-loaded sub cabinet from
www.creativesound.ca these guys up in Delta, BC have lots of cool stuff. Cut a hole, stuff it, mount the Koda and you are done. A wonderful little sub for not much dough.