ZD, you summarized my inquiry better than I and hit on one of the issues that has been in the forefront of my thinking, the factors associated with timbre. Even with my age related hearing issues, in my uneducated way I still believe that those frequencies that are beyond audible have some importance in overall sonic quality. To some extent I was able to demonstrate this when I added the EQ's. When setting them up I used my audiogram to establish a baseline slope. In this exercise I pretty much ignored adjusting those frequencies above about 8000hz because they were beyond my audible range. At first I thought that the equalizers compromised my sense of timbre which is one of the most important factors in my listening enjoyment. Before I removed them from the system, though, I continued messing with them and discovered that boosting those frequencies above my way upper limits improved the sound to the extent that even I recognized it. You also mentioned that tube amps, out of hand,are not necessarily the answer because some can also be bright, a fact that I had already discovered a couple of years ago when I traded my Rogue Audio Sphinx for an integrated tube amp which was so bright sounding that I kept in the system for only 2 weeks.
Also, years ago I thought that my sensitivities were related to the higher "tweeter frequencies" and I experimented with tweeters to no avail. In the process, though, I discovered that good tweeters seem critical to timbre. As stated, my sensitivities are related to frequencies in the 1400 to 1900Hz range corresponding, on a piano, to somewhere above middle C.
Lostbears, good suggestion; sometime today I will reinstall one of my tube DAC's to see how much that helps. I should have been a little more clear, though, regarding the fact that I'm looking at the possibility of switching to a tube based power amp based on advice from a very well respected audiophile here on Audiogon.
Detlof, thanks again and to answer your question, the upper middle frequencies produced by the piano don't seem distorted, just harsh to the point that at normal listening volumes (I know....whatever that means) it can actually cause me to wince.