36/18 room

36' x 18' x 10' = 6,480 cu.ft.

IMO, dual 12s at a bare minimum. Dual 15s would be better.

Kind of depends on what your goals are - as far as how much extension (how low), and SPL (reference required, or you listen at low levels).

Good thing the ceiling isn't 9'.

You'll need two 12"s at a bare minimum, and even then you won't have significant headroom. I would go for two ported 15"s in that place.

It looks like your budget took a hit. From those I would get the Dayton subs. You need as much output as you can afford in that room.

Dual HSU VTF-15Hs would be sufficient or maybe dual Outlaw Audio LFM-1 EX

Of those, I'd go with dual PA-150s.

For perhaps not much more, though, you could get dual Rythmik FV12s. If you haven't already done so, contact Rythmik - or post a question in the Official Rythmik Audio Subwoofer thread - and see what Brian (company owner) has to say about dual FV12s in your HT space.