I couldn't disagree w you more. I've heard way more awful sounds in big/custom spaces than I've heard superior sounds in small/non custom spaces.
I'll take Audiophile Bill, Montesquieu Tom, UK Paul, Blue58 sounds over any number of grander more expansive rooms/system complexes. Even Purite Keith with his Cessaro Liszts in a typical London Victorian living room, other than one flaw, kicked total ass.
These are all superlative sounds on so many levels in totally manageable domestic situations.
--
Where we *can* agree is that the room (acoustics/power/noise) is king, and the best sounds are holistic ecosystems, where you can't divorce the system from the room or vice versa.
But this fantasy that you need an enormous custom built room is just that, a fantasy.