[AB]

...unless I'm imagining that, too. At this point I have no idea what to believe, except that my very, very expensive rig sounds positively unlistenable, and I'm pretty-well exasperated with the whole flippin' thing.

Step away from the stereo. SLOWLY.
Go into another room and find something else to occupy your mind. Go for a long walk. Go for several long walks.
Return to the problem only after you have had a few days away from it.
Then break the system down and rebuild it.
Once it's back together listen to it with an open and fresh mind - as if you are hearing it for the first time.

[JRace]

Step away from the stereo. SLOWLY.
Go into another room and find something else to occupy your mind. Go for a long walk. Go for several long walks.
Return to the problem only after you have had a few days away from it.
Then break the system down and rebuild it.
Once it's back together listen to it with an open and fresh mind - as if you are hearing it for the first time.

Very good advice!

[dogorman]

I agree, too, very sound advice, and I'm taking it. One thing, though: will there be any interest in all of these symptoms when I come back, or will everyone else be all, "Oh, gawd, not THIS guy again."

The front-apron vibration thing, in particular, struck me as one of those bizarre symptoms that carried with it the potential for spot-diagnosis of the, "Oh, well, you've got a faulty input diode in your transformer catalyst" or some-such.
 

[AB]

I agree, too, very sound advice, and I'm taking it. One thing, though: will there be any interest in all of these symptoms when I come back, or will everyone else be all, "Oh, gawd, not THIS guy again."

I can't make any promises and I can't speak for anyone else here. 

The front-apron vibration thing, in particular, struck me as one of those bizarre symptoms that carried with it the potential for spot-diagnosis of the, "Oh, well, you've got a faulty input diode in your transformer catalyst" or some-such.

Sounds like your chassis has a poor ground.