probably off my rocker here, "but"
i sometime mess around with some older(50's/60's) lower power tube pcs, and when first start up i always start with a variac. slow, low power. i started to realize that most all tube amps will generate sounds at a lower power. some actually start to generate music at 70/75 volts,(not a perfect sound) but good enough to tell that the unit was going to work without the magic smoke . i realized that around 100vac the beginning sound was good enough to sound ok for my old snuff box ears(older folks might get this) also actually drops transformer temperature, and i feel with less trans stress. oh, less heat by far. with a pair 6l6 amps, 50w quad each running at 100v did make a lot of difference in room temp. but still these are my winter amps, they will come down in the spring.
you can hang me if i am wrong. so far it has worked for me. my opinion less power in, cooler internal parts, maybe even longer tube life, a lot less heat. i have been doing this for a few years with no noticeable difference in sound quality (snuff box/can)
by the way usually i don't push the amps very hard, most time at lower volumes.
16x16 room, between 85 / 100db as loud as i like it, until after a little numbing then sometime move volume up a little. that is a lot of talking too much but(lucy said splain yourself).
sorry for being long winded