I'm probably dumb but... I regularly play music at 15db above THX @ 10ft when I'm in the "spirited" mood, which is often!
(1-5% system power)
That's about ALL the treble I'm WILLING to tolerate though... and ONLY when accompanied with equally hot bass.
My system can sustain these levels all day long.
When guests are in the HT I turn it down to -5 to -10db, as I've discovered that that is about all the treble they can handle long-term without complaints.
Most are willing to tolerate a 30 second demo at +15db, sometimes a few whole songs.
To your average joe that usually gives them a grin from ear to ear, something they will likely never experience again (not with good SQ at least.)
When I reach 10% power on the fp amps, the walls and speakers are on the verge of flying apart or smoking or bottoming out.
I'm almost-certain that 50% power would cause all the subwoofers to blow up (depending on the song);
and the mids and tweets would be dead by 3% power, on their respective fp amps...
But my system is FAR from conventional, so your figures may vary a lot...