Looking for the "better sub"

I have Magnepan 1.6/QRs and would like a sub sometime soon to fill in the low end.
Subs suggested to me have been as follows...

Vandersteen 2wQ....problem with this sub for me is most agree I need two from the start for my 25X15 room.
JL Fathom 113....I would have ordered one, but no high level inputs turns a great sub into a home theater product in my eyes. They blew it.
Martin Logan Depth....still a frontrunner. Quick and musical. And one works well enough to get started.
REL....Still looking into these.

So I guess I'm looking at a budget of about 2K...a bit more or less. Anything else I should be looking into beyond the above? Please comment if you've heard the models above, which (except for the Fathom) are well known for working nicely with Magnepan panels.

Thanks!

R