Trevor, there's a good treatise of this at the following link:
https://www.audiosciencereview.com/forum/index.php?threads/analytical-analysis-room-gain.23211/The bottom line from all of this is that room gain rises at 7 to 12 dB/octave starting at the frequency where the longest room dimension is a half wavelength.
Incidentally, this is why a 500, 600 or 800 does not work in my living room but a 125 does. The 125 rolls off enough that room gain brings it up to flattish on the low end. The sealed subs gain too much and go boom!
Having said the above, someone whose hearing is bad down low could benefit from the sealed subs. Alternatively, with sub EQ - which I don't have in the living room - the sealed subs may work better than the 125.
