So, I did it.
I've actually had the amp for a couple of weeks, but some of the tubes were crushed in the shipment, so the thing literally sat there staring at me for at least a fortnight before they sent me new tubes (matched quartet of Mullard EL-34, so-called "The Master Valve", which, in this German amp, is too classic). Anyway, that just gave me lots of tie to clean it. Still a bit of work to be done, but aside from the right neon light being out and a knob on the back needing to be reglued, nothing is wrong with it in the least.
And, by the way, the amp is:

The Hughes & Kettner Mark II Triamp. Billed as "The ultimate tube head". Each of the three channels has two modes, essentially making this a six channel amplifier. 100 watts. Superlative cleans to dynamic blues to better-than-Marshall Marshall classic crunch to ultra-tight and incredibly well-defined high gain distortion that retains a lot of pick attack and crackles violently. Takes the flexibility of a Mesa and fuses it with German amp (i.e Engl, Framus, Bogner) clarity and spank, minus the boxy and ubiquitous crunch of the former and the sometimes too-clinical coldness of the latter. Pretty much, I think it's the best possible amp I could have found, for my needs.
The signature model of this is for Alex Lifeson, of Rush. For him, they didn't change any of the circuitry--they just changed the color of the neon and the tolex covering. In short, there wasn't much to improve upon, internally.
New, this is 3.5K. Used, it is usually 2K. Mine was 1299. Came with a 7-button footswitch, built-in direct out, half-power switch, and is midi-compatible. This has been the year of acquisitions: three gear items in a row purchased for at least 40% below true market value.
Oh. And the H&K glows blue. So, like every other tool with one of these, I had to take a picture of it with the lights out.
Still need a matching cabinet, but those can be had for around $500, and in the meantime I've got a Marshall 1960A, which seems to do the job nicely so far.
I've tested this some in the studio and it sounds phenomenal. Not sure that I'll use it too much, since I've already started with a Powerball, but will try to sneak this in during some clean passages or on the doom track.
Mmmmmmmmm.