Lowrider: I'll try that idea on the ICs, but not too optimistic. Already attempted a couple variations along those lines, with little result, but I'll dig deeper into my cables (BJC or Better Cables or old vintage Monster seem likely candidates). Stay tuned for a report.
Erik: Thanks for the insights. After 45+ years of playing percussion, and several visits to the audiologist, my knowledge of my condition is as stated above. When playing, I now religiously use hearing protection (isolating Shure ear buds, currently). I run them thru a multi-output pro headphone amp (presonus) with volume controls for each output. I try to keep the levels reasonable when playing with my combo in-studio, and I use more mundane ear plugs for live gigs. This all helps, but the damage to right side hi freq. is real.
All: I think much of my issue is reflected by the tension between seeking neutrality in the gear, and needing brighter highs given my story. Put differently, and more usefully, I wanted to avoid listening fatigue, which I get from overly harsh highs, so I overcompensated (a lot) by inappropriately combining gear that ALL boasted "laid-back sonics," per Lowrider's comment on cables. In my case, the Sim Audio, Marantz, Audience, and even the Totem Hawks (though less so) combined to over-soften my highs. The result has been muted highs that are a particularly poor fit to my personal situation. Please comment.
Other miscellaneous news:
(1) Took the Moon W-5 in for service today. It needed a couple minor fixes anyway. The senior tech was deeply skeptical of the high freq. issue residing in the amp, as I previously noted in an earlier post, though he admitted a messed up capacitor could conceivably play a role.
(2) Room conditioning fans: I added bass traps to the corner nearest to and opposite the speakers. So far, some minor differences are apparent (better clarity at the low end, but it's pretty subtle). I need to listen more extensively following this tweak. No effect on highs detected so far. I used 72" of cloth covered medium density foam cylinder. Actually looks ok.
Thanks to to all for hanging in there with me on this issue.
-B