Opinions before purchasing

The size of the room has no bearing on whether a speaker can reach a certain Hz. A speaker, of any variety, puts out certain frequencies regardless of whether they're in a bathroom or a 6 car garage. In a room that size, one sub will be fine and if properly adjusted, will get down to it's stated frequency, as long as the manufacturer is accurate with their measurements. 

May I ask, you want to listen music as well with your system?

Then you better organise a 2nd pair of old but big speakers + simple dsp device such minidsp2x4hd and use this combo for ADD'L music bass reproduction only. Subs can never achieve this (even expensive ones such REL since drivers are too slowly).

SQ of your 2.0 system stays extremely superb then.

Greatings

Jason's talking about the room resonance, which reinforces bass output.  Of course, almost all speakers will roll off below that room effect.  That is the whole reason why DSP is particularly useful for low frequencies.  It's not that the speakers are that bad at producing bass, it's their inevitable interaction with the room.

Of course, there are always trade-offs.  It does add cost & complexity, and DSP requires that analog signals be digitized, if you use any.  That may be more trouble than it's worth, given that you're not that interested in the bass effects.

I've tried a bunch of things in my HT, and the best is a Magnepan system (current). I use MMG-W mid-treble units for everything but the centre, which is a Quad, but the MMG-W would work for that too. Add a DWM woofer for L and R channel (as  I do), and you have Nirvana. Bryston power is perfect.

YMMV.

1000-1500 dollars? 
For speakers? 
at that price point please save your money until you have a few thousand.