I don't think it is a matter of a tube amp being overly warm. This is based on an old preconception of what tube amps are - these days in any event. They are to my ears much more likely to be overly bright and as my old friend Joe calls it they sparkle.
In truth like all things there is a spectrum of warmth and coloration amongst tube amps as well as solid state amps.
I fairly certain that if you are 35 or older that you have heard a warm SS amp.
Harken back to the SS days of the old Japanese Luxman, they were warmer than warm, hot by that measure. How about the current sound of Accuphase, is that stone cold nuetrality? To me they are warm, even as far as a highly pronounced warmth and charge real big money for the priveledge of hearing that style. I am fairly certain they do not have a tubed product in their history since Kensonic to today.
I am utterly sincere when I tell you that some tube products a super quick almost analytical and tend to shine.(for one, someone mentioned Atmasphere) Although the real value peculiar to tubes alone when well implemented is the incredible layering of the music. The kind of staging a good tube amp can give you is unmatched intruiging and very involving.
Why do I say this? Because I paid what I consider a big chunk of change for Golden reference or whatever the top Gold Cardas was 5 years back, used yet, to offset the sterility of my SS monoblocks. It worked out well but even moreso after I bought tube power amps. I used it between the pre and power in both situations and I still use those Golden --- by Cardas and I am loving it more than ever.
I can assure as the owner of 3 vintage tube amps that you can't begin to compare how tubed amps sounded in the golden age of HiFi, circa 1955-1965, that is BTW also what I mean by vintage, not 1985. Versus a modern tube amp circa 2009. I wish you could take a really well designed, well liked, 1962 Scott, Fisher or in my case a Sherwood amp. or real theatre amps at the advent of modern audio, not stereo that had to wait until the golden age.
I mean the first widespread use of the early 300B amps Western Electric being the archetype. You will point to the amp and say. Don't you hear what I hear they are soupy, slow, dark, rolled off etc. I will then tell you, yes I agree it is true. I will ask you listen to Dehaviland, Rogue, Jadis, Wavac, ARC, Manley,some C**ese amps etc,just not Conrad Johnson. I ask you, do they sound the same as the older amps? IMHO, No not all. Do they even sound like each other ? No not really. I prefer to keep it real.