Subwoofer recommendation for swarm


I want to create my own subwoofer swarm am looking for reasonably priced units, want to stay under 2K.  Recommendations welcome.  My room is 20' L X 13.5' W X 9' H. 
zardozmike
I just finished putting together my subwoofer swarm.  4 12" drivers spread throughout the room.  Doing the first listen now.  It's totally changed my system for the better, I don't even recognize it. 
What low frequency response are you getting with the four subs? I have a 12’x18’x 9’ room. Would like to see 22Hz if possible . Acoustic treatments installed also.
I haven't measured my frequency response yet, but will be doing so soon.  I'm still experimenting with location. Need to do that by ear and takes awhile. 
For anyone considering a swarm setup, SVS currently has their SB12-NSD subs on sale for $399 each with free shipping.  I have no personal interest, just a good deal in my opinion.  I have one of these that I use in my office system and it's been a good performer.  I also own subs from PSA and Rythmik.