For a large space like the one initially lined out by the OP (or be that even a smaller ditto), serving home theater duties to boot, I'd wager to keep the thing of it all the most "musical" - i.e.: with low distortion, effortless and smoothly distributed bass - is to go with two or more big, higher eff. subs. Many seem to be hellbent on the "multiple smaller subs vs. fewer or only a single big one" division. For Pete's sake, what's with the self-imposed limitations? Have your cake and eat it too with a bunch of large subs like the ones from the reasonably priced and quality items PSA, and make them no less equipped than with 18" diameter woofers. These are high eff. pro drivers with a moving mass to cone diameter and motor force ratio that in no way makes for "slow" bass, contrary to some high moving mass, very low eff. (<85dB's) woofers meant for ultra small sub cabs with a bass reproduction that never really "gels" with the mains. Yes, very generally large, high eff. subs to my ears sound somewhat more musically "right" and well-integrated, because you don't sense they're using any real effort reproducing bass with their large diameter cones that barely move. Sonically in some regards REL subs are one of the more notable exceptions from the small cab/low eff. "camp" being not least they don't try and squeeze out infrasonics from their designs, that would have otherwise necessitate a higher moving mass in the driver and thus resulted in even lower sensitivity and likely bass lag. But, again: big (higher eff.) subs are not only viable for music reproduction; they would seem wholly essential if you ask me, while providing for a very worthwhile impact watching movies as well. What people won't do to avoid size in subs, and the hassle this has a tendency to bring with it (sometimes unknowingly, because they haven't heard the difference). It may even come down to large size being judged as "not looking cultivated enough," or "too brute for hi-fi." 🙄 When you got the space, use it. Bass properly sized/scaled is all the better for it.