Thanks.
I decided to go ahead and make it fail so just after posting that I bumped it up to 105dB and about 5 minutes later it went into protect mode. Never noticed any distortion. I let it cool down for about a minute and turned it back on and am now playing at a more normal for me anyway 80dB average.
I played my Denon 2807 that loud once but not even for 5 minutes but it was un-listenable above about 95dB. The Onkyo sounded fine right up till it stopped sounding at all.
I imagine if anyone was going to be playing 105dB at 11.5 feet their going to be buying an amp anyway. It got warm enough that I would recommend good ventilation but I’m not seeing any problem with how it performed.