Completely understand and agree with the things your saying
At the same time Ive recently done a musical theatre show in a smallish theatre about 1.5x bigger with quite a high vaulted ceiling than these dimmentions and I had 2x 250w rms 8 inch main L/R at 95db sens, 1x 200w rms 6 inch centre at 93db sens and 2x 1000w rms 12 inch subs cant remember sens for these. Often runing all of them close to their maximum in some of the songs and whilst it was loud it was never close to unbearable and I would have liked more at times
I think we need @Thealchimist to clarify exactly what type of room this be, how loud it will be and the type of music that will be played to get us all on the same page here