Outlaw LFM-1 Plus looks good to me. I'm thinking about buying one for someone with a pair of M3's and no other speakers.
I ahve a Denon 1910 (791 equiv) and I *just* set up my LFM1-Plus last weekend... one warning, the LFM1-Plus is a powerful unit. Though my room isn't big, weighing in at 10x14x8.
I hooked it up, set it to max extension mode (down to 18Hz) (figured I didn't need too much volume in my room) and set the Volume to 4. I put in Pixar's "UP" and went to the Storm scene. I swear the pictures almost jumped off the wall!
Turned the Volume on the sub down to 3 and ran Audyssey. Even with the Sub's Master Vol at 3 my sub channel gest set to -12.5dB.
I still need to tweak the position, volume and recalibrate before I comment on tightness and quality of bass but I can certainly vouch for the fact it goes LOW and does it LOUD. From what I understand Front firing vs Down firing makes no difference. Down Firing is better if you have little kids that might put things in ports though...
Also, the Denon 1910 puts my movies at an uncomfortably loud volume at -15dB on the Dial. I imagine the 591 will fill your room just fine.
However, having said all the above, your room is ~5100 cubic feet and mine is only 1100 so you have a lot more space to fill. Really I just wanted to blather about how happy I am with the sub.
snazzed
