I finally got around to trying a G.A.S. Grandson on the ESLs, and their mojo is back! I am astounded at how much the Grandson sounds like the Luxman and PrimaLuna tube amps. It has a crystalline treble, perhaps not as liquid, but the separation is what amazed me - airy, spacious, and open.
At first I was afraid of trying them because of their age, so I took a look:
Looks OK, so then I tried them on my DIY two-ways, watching for smoke and listening.
Then the Quads with lamp cord, still no smoke. Finally with the Goertz wires, and the same setup but replacing the Marantz MM9000 that I was using for temporary duty. Well, I should have done this long ago! I think that I've solved my backup amp problem, so I can take my time fixing the PrimaLuna, which I still have hopes for getting going again. Or the Grandson could serve as a permanent solution even. It's that good with the Quads, to my ears so far. Extremely revealing. The two-ways were oddly diminished in comparison. My pride took a hit, I must admit. I might even have to open the last of my Lepai 2020A+ chip amps to see if it is as particularly suitable for my two-ways as I remember it to be.
Back to the point, the separation of the Grandson/Quad combo reproduced a momentary bit of sibilance from my getting-on-in-years Benz Micro as sonic artifacts located in front of the speakers. In my setups the Quads have always imaged from the speaker plane backwards, never in front. I happened to visualize the bit of sibilance as if it was coming from clusters of crystals in front of the program image. Two feet long, officer.