Michael--
"Tube amps" cover a lot of territory. Some are great; others have been less so. But let me assume that your experience is with the best of the breed. No doubt what you appreciate is the sense of palpability and immediacy that the best tube amps can provide, and the spaciousness they can reproduce from a high caliber recording. That certainly is what I have appreciated.
I've had several of the Spectron amps, including the SE (currently being upgraded to Mk.II) and the Musician III has had the remarkable effect of making me utterly uninterested in searching further for the mythical, holy grail amplifier. My budget had plenty of room for car-priced amps, but the Musician III is so extraordinary that I simply can't drag myself out to compare amps anymore.
As a former symphony musician, I think I have a pretty good idea of what real instruments in real space sound like. The Spectron amp gets me closer to that than anything else I know of. Tube like immediacy and palpability, coupled to absolutely ruthless control of the drivers by the amp, so that the speaker and amp act as one. The delicacy of well-recorded strings is, well, like the delicacy of well-played strings. Voices have heft and presence. Bass is as tight as it was in the recording venue. And if the recording engineer captured the space of the venue, there you are.
Best,
Jonathan
The Spectron amp is utterly indifferent to tricky loads. Its an amp for all seasons.
Get one, and you can go back to listening to the music, which is what this is all about, no.