^ 4800 cubic ft is not a small room. Most around here would recommend a minimum of two ported 15" subs with LF extension down into the teens. A pair of ported 18's even better.
Like yourself, I had to contend with WAF size restrictions and landed on the E15HP's. This was before the HP2 with the 1000watt amp came out. I would have went that route had it been available at the time. If your goal is high fidelity music, you wont be disappointed with the E15. I have an open house with over 20K ft cubed so pressurizing the room for movies is not even a remote possibility. But that was not my goal, so it was a compromise I was willing to make.
FWIW, now that the Mrs appreciates the sound quality from the E15's, she got over the size. She would not go without sub's again she recently admitted. I however, do have a bit of the What If's about not going ported.
Rythmik gives you the ability to go ported with its output benefits, but retain the sound quality as good as, or better than other sealed models for music.
Probably not much help, but some food for thought.
5.1: Power - Denon 4308ci, Fronts - Def Tech BP9040's, Center - Def Tech CLR 2000, Surrounds - Def Tech PM1000's, Sub's - Rythmik E15HP x2, Display - Panasonic TC-55AS530U, TT - Rega Planar 2 w/ Dynavector 10x5