If you don't mind used, you should put the MB Quart VS1B (in
Elsberry or
Maple finish) on your list. Its rated response goes down to
35Hz (Edit: I think that was for the VS1F.
Sound & Vision says -3dB at 50, -6dB at 43). I have the VS05B, and occasionally when I turn my subs off after my daughter goes to bed I have to check to make sure they're off. Beyond that, they're some of the most neutral, transparent speakers I've ever heard. It would be worth contacting that seller to ask how much shipping to you would be. (
Google translation of the maple offering. They both have pretty much the same description.) If the lower price makes you pause, bear in mind that they retailed for $4000 a pair before the Maxxsonics takeover.
There's also the German Maestro
Linea-S B-One, with a rated output at 38Hz.
US Retailers. German Maestro is where MB Quart's speaker designers ended up after Quart's demise.
Or the
Salk Silk has a 42Hz bottom end.