Transients hurting my ears on hifi solid state amps

I didn't indeed react to that part in detail. I have been to an ENT and although he could see that subjectively I was sensitive to loud noises, there was nothing physiologically wrong and nothing that could be done from a medical point of view. I've been more sensitive than average for as long as I can remember, feeling the need for earplugs when others didn't, struggling with headphone listening, etc. I play instruments and have been in bands.

When I had my bout of needing to see an audiologist it was a sudden onset, and it went away in a few weeks.
So I suppose if the amps that were good in the past are still around it would be worthwhile to use them to see if they are still good, or whether the hearing is now sensitive.

As said, listening on a speaker system, I never had this issue before going to higher end models and my theory was that the higher precision and faster transients translate to a higher perceived air pressure.

It is sound pressure, not air pressure.

I doubt that the amps are any “faster”, as most amps play 20kHz just fine, and nothing is going to arrive faster from a 2kHz signal, than a 20kHz signal.

And if it is grating harmonics that spray into the upper frequencies then that could be cured with the amps that were mentioned as being good sounding.

But a fishbone diagram would include things like:

• ears
• distortion signature
• clipping affecting distortion signature

so we sort of need a way to ameliorate or exonerate the most probably causal mechanism (candidates).

Once we know the mechanism, then we can determine the best equipment to use to mitigate the mechanism.
(But I do not go straight to power cords, power conditioners, now cables as mitigation mechanisms… I like to take a more direct approach than a “buying festival” to play “pin the tail on the donkey”, where I am hoping to hit the solution by accident or chance.)

Your comment that "toe-in does make the sound brighter" left me wondering if that was due to higher frequencies being more directional, as I understand basic acoustics. Being aimed towards your ears would account for the "brightness." Pardon me if this has already been suggested.

It is highly likely that power level is your problem. Even at low volumes, moderately efficient speakers can benefit from higher power and it can significantly reduce fatigue.

I recommend looking into separates. Pre-owned Parasound A21 amps can be found for ~$1200. Their distortion profile is primarily 2nd order, which is very rare among amps below $5K, and output enough power to provide plenty of headroom for nearly any speaker. Pair an A21 with a low distortion preamp like the Topping Pre90 and you’ll have a very smooth and low-fatigue setup that can takes up little more real estate than an integrated.

Another thing: if you’re one who typically indulges in adult beverages during your listening sessions, practice cessation for a few days, and try listening earlier in the day when you’re alert and rested. Listening while already fatigued just accelerates listening fatigue IME. Alcohol tends to have that effect as well.

I remember learning that our ears are most sensitive in the frequency range where we are experiencing hearing loss. Apparently it's common for the high pitched voices of children to bother some grandparents. ;-) 

Thanks @holmz for the various very good points and suggestions. Just a clarification on one point, as this is one of the things I'm trying to understand here:

I doubt that the amps are any “faster”, as most amps play 20kHz just fine, and nothing is going to arrive faster from a 2kHz signal, than a 20kHz signal.

With fast I mean that the transients, the typical example being the hit on a snare, are quick and powerful. So in a graph measuring the sound pressure, the peak would be higher and narrower on a "fast" amplifier and lower and flatter on a "slow" amp. The sound is more compressed in a "slow" amplifier and thus the hit of a snare or the initial transient of a piano note will be felt as softer by the ear.

I understand that there are other factors discussed that heavily influence the perception, but I do believe that this is part of the equation. Low powered amplifiers would in my understanding be therefore more suitable to avoid the problems I've had. It is not so much sustained notes that cause issues for me, but the percussive sounds and initial attacks on many instruments.