Go with JL F212s and save money for room treatments and bass traps.Think about ease of setup and integration using a spectrum analyzer to match it to the rest of your system.
Two JL F212s verses two Velodyne 18 plus?
I have a room 13.5 x 24 dedicated home theatre and listening room. Presently I have a Velodyne DD 15" sub. I am looking at going to a two subsystem and have another application for my Velodyne DD 15. I am considering two JL F212s or two F113s or two Velodyne 18 plus. I have been slightly underwhelmed with the single velodyne DD 15. The rest of the system is Anthem D2v, Classe 5200, B&W N802s, HTM1s and B&W side and rear speakers. I run a rotel amp for rear speakers.