Help finding a Sub w/ quick punch down to 20hz

I believe all the Velodyne Digital Drive Plus models are rated well below 20 Hz +/- 3dB.

I replaced a single Digital Drive 18 with my third generation of Velodyne, two Digital Drive 12 Plus in my two channel system. It's a largish room with a vaulted ceiling. The two smaller subs added to the sound stage as well as the rooms bass nodes have lessened.

Check out Seaton Sound. The website, like so many ID manufacturers, leaves a lot to be desired. However, contact him directly and he will get you the information you need for your room and your budget. His subs are highly regarded by many.

Surreal Sound's Constellation sub-woofers will do it. You can custom select the number of drivers based on the volume of your room. "Dipole bass with an attitude" is their tagline, and it's absolutely true. See:
http://surrealspeakers.com/
.

09-02-12: Johnnyb53
The REL F110 is about 13"x15"x17" and is good to at least 25 Hz.

Oops, I meant the JL Fathom F110, but you guys probably figured that
out by now.

Some really good sealed units have been mentioned already. The JLs are nice if your budget allows. I have a pair of the HSU ULS-15s in a large, open floorplan. They offer plenty of low end in my hard to tame room. I am employing the use of an SVS AS-EQ1 to take care of some peaks and valleys. I went to the HSUs from a pair of SVS SB12s. While the SB12s didn't have the headroom I needed, they did sound great and integrated well with my mains. Their new SB13 looks nice and should get you the Quick punch. I'm just not sure it would get you into the 20s.