I re-read you post and noted that you are, or were, interested in downsizing. I recently downsized my A21 to a buckeye amp that has output power about the same or even a little better than the A21. In terms of sound quality, I did not feel there is any difference at all. I also have an anthem MCA amp used for my HT system's FL/FR channels and I never felt any harshness at all. So, I do feel you have a strange case indeed. If it is the speakers, then the same harshness should be felt with the other amps and preamps you auditioned, so again it is really "weird" as you described it yourself.
Regardless, if you ever have the itch to downsize again, I hope you would consider one of those little Hypex, or Purifi amps a chance. Your AVM90, or 70 (not sure which one you have) should have more than enough voltage to drive them.
See how much space you can save, if that matters:
I believe the A31 may be slightly bigger than the A21, may be not. The Purifi ones tend to be slightly larger.
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