In my experience, detailed, extended, and powerful subsonic bass (and up) is possible from 800's even at 'normal' SPL's, but especially at elevated SPL's (95dB+).
Their ability to let me feel the thump/concussion/rumble in my head and body, that's in the music, is remarkable.
Yes it does take much fussing with dialing in the entire system, but the musicality, tonality, spatial cues, stability of the acoustic presentation etc, is better than any other I have ever heard, including and especially with speakers.
A speaker based playback system that can 'properly' reach to even 25Hz let alone to 15Hz (or lower) is, while possible, VERY rare and expensive.
Yeah that sounds like an eye rolling statement but as contrast the absolute worst SQ I've ever heard was from a ≈60K+$ system.
It had NO bass down low, except for it's 'one note bass' response, and nothing else, the mids were dead, flat, receded and barely even 2d, and the top end was screechy.
IOW it's not just about the synergy of the gear itself but also the remainder of the setup in it's entirety.
The thing that really amazes me about the 800's is that while they are not perfect (is anything?), they scale so well and continue to reveal subtle nuances with increases in inner focus and details (especially in the very bottom end, and as they couple with that instruments upper frequecies) as the rest of the system is improved and the signal handed to them becomes less 'veiled'.
Just my 2¢
JJ