There are several angles to it.
1) waveforming, DBA, SBA and ART - all the sytems that aim for controlled low decay objectively require much more subwoofer real estate. I still remember how I was surprised after having 8x18in subs installed in DBA config. I was expecting bass inferno, as i replaced 7x15in subs, but it subjectively felt as less bass, Half of the output is gone, as rear wall acts as absorber. Also energy is not bouncing around for 1 second with all the resonances, that are usual in standard setups.
2) This is why Pressurization is so important WF feature - it allows lowest bass to be addtiive. Usually 30+Hz every system has abundant energy, what matters is 25Hz and below
3) I had a chance to visit some American HT;s with insulated drywall walls - and you can not keep bass in, and also need much more subs to get to the same result as we get here in Europe with our 30cm reinforced concrete walls [in my case] - gives you 6dB room gain minimum, compared to drywall.
And I think - only more is enough, in terms of bass capabilities - I am not basshead myself, I think my bass preferences go towards clean, controlled and tight, but I also appreciate to have reserve and overkill. Nothing is worse than sub bottoming out, because of missing woofage.
20.000W, 8x18in subs, 32 sqm, feels about appropriate in order to be far from limits of the system.