Hi,

Either choice will provide plenty of dB's of quality bass and will be more than enough to fill the space you described (1787.5 cu. ft.). Going with two subs should pretty much guarantee you the ability for nice, smooth bass response throughout the listening area with appropriate placement.

The main benefit of the LFM-1/LFM-2 combo would be a bit more extension and headroom. I am not familiar with the Def. Techs so I can't offer you any personal experience there, but the PF-1500 has pretty deep extension, no? 14Hz or so if I'm looking at the correct brochure online?

I am definitely in the "you can't have too much quality bass" so If it were me (and I had a generous budget), I would be looking at an LFM-1/LFM-1 Plus combo with an SMS-1.

Based on the options you've laid out, my choice would be LFM-1/LFM-2, all the way.

Nice HT setup, by the way!