Interesting article. An MKH-20 would be a good choice, but alas out of production and no more affordable than an Earthworks.
I did find the Behringer ECM8000. Very affordable an rated FR goes down to 15hz. At less than $50CAD, that is worth a shot at catching some thunderous rumble.
Of late I have been recording all my nature ambience in ambisonic using my Ambi-Alice (thanks, Jules), and a Zoom H3n, but I would like to throw in a channel of subsonic to give the subwoofer something to do while it's raining ;)
Mark Day