Okay, I do have a suggestion. The first thing that popped into my head was the SVS MBS-01, but they cost $950 + shipping and only go down to 48 Hz. So, I'll suggest looking at the Aperion Audio
Intimus 6B. They also are only rated to 48 Hz (-3 dB), but a pair is $700 including shipping. Also, Aperion will pay shipping both ways with no restocking fee if you decide to return them for whatever reason - so there is no risk to you at all to try them out. I know they don't go quite as low as you were asking for, but I thought that I'd throw them out as a suggestion. People that I know (personally and on this forum) have been quite happy with that company.