While a pair of Rythmik F18’s is undoubtedly awesome (I say that being familiar with the F15), a quartet of smaller subs (say, the F12) may be even better. Place two of them as close to your listening position as possible, to maximize " visceral-ness".
The F12 is available with either an aluminum cone, or a lower-mass paper one (the F12G). The F12G has been optimized for music, the F12 for all-around use. Get two of each!
If you find the dual-opposed design---popularized by Seaton---appealing, check out the newish Rythmik G25HP, which I would much rather have. The Seaton is just a couple of woofers in a box; fine for home theater, not for music.