How big is your room?
The Plus actually goes down to 18 Hertz in Max extension mode.
For the time I had the LFM-1, I loved it! it could shake the room like no other sub ive owned before, the only reason I returned it was because I wanted bigger
You cannot go wrong with the Outlaw, two of them would be a pain to setup, but would give you a ton of bass when calibrated properly. I personally think you would be fine with one LFM-1 Plus.
Have you ever owned a higher end sub before?