Hi V,
My two cents here; I think You have a little dilemma here, that's why You've asked WBF. Due to Your tinnitus and high frequency sensitivity, the amplifiers You would consider High-End would not suit You and what would suit You better are not considered high-end by many. What I have experienced is that; the better the amplifier gets, the more open in the highs it becomes, which means, if there is information on the high frequency range, the amplifiers conveys it; to be exact; whichever frequency there is information the amplifier conveys it. So I would recommend You opt for more a "warm / musical" amplifiers, than a "natural" ones.
So, from my own experience absolutely not Gryphon old models (Antileon etc.), they are all harsh. New series are commented to be more natural but haven't had first hand experience, only dealer/ show experience. As many commented, when You say "natural" first names to pop up are European and more specifically Swiss amplifiers; CH, Soulution, Nagra.. From these three, Soulution might suit Your condition best in my experience both first hand / dealer show demos mixed. In case of CH; A1.5 would be way better than M1.1 for Your case.
What I would recommend more in Your case would be Accuphase > Luxman = McIntosh. They are to my ears, more natural than the regular US amplifiers (Dan, Krell..) but slightly more rolled off in the highs (I guess because the Japanese design philosophy leans slightly less high frequency domain due to their roots in big horn speakers). If I was to chose just one amplifier for You, it would be McIntosh MC 462. Mc's are strong in low-mid band; which means You would easily saturate Your room with low & mids so would turn the volume slightly less i.e. less highs. Side note: Pass Labs especially the former .5 series might be for You but that's a very close call. Also; You can easily try the Accuphase sound to hear if it suits You. No need to go for a big, flagship power amplifier at first. Any integrated amplifier (even older ones) above 4 series, 5 series and special edition ones would perform over 90 % their dedicated power amplifiers would do (2xx and 3xx series Accuphase would not perform in-line with the rest of Your system). Between purchase and selling of one You wouldn't lose few hundred bucks or many local dealers have them in numbers waiting to be sold second hand, one You have good communication with, would happily consign You one.
What I would recommend though is; definitely stay away from silver cables and go for all copper. The better quality copper cables (Transparent and Kubala Sosna in my case) would suit Your case better. Silver cables tend to 'shine' the highs, when that's what one is looking for.
Happy listening..
