.... I don't think of it as warm; .....
When I hear tube sound described as warm I generally think of design or implementation problems leading to poor quality sound. Tubes running outside of their best bias and voltage ranges; old worn out components; out of spec resistors and capacitors and bad power supply design.
I don't hear the 2nd harmonics that SE tube amps produce as warm. Maybe some define warm differently than I do; but a well designed and built SE tube amp should have a clear, detailed sound with harmonics that some (gasp) enjoy. A PP tube amp will have less harmonics and should still be clean and detailed.
I have heard a cheap little cube style tube amp that sounded warm but I did not see that as a good thing. The music was lacking life and detail; I think it was just a lot of regular noise and not harmonic distortion that was muddling the sound with it. Many people seem to think that is the "tube sound". My current tube amps sound nothing like that.
I think a bit of distortion and the harmonics may mask some of the harshness that some music has. I did one of those online tests to see if you can tell the difference between different resolution sound clips and I was able to pick the higher resolution ones pretty often by picking the clip that I didn't enjoy.
I have both and while tube amps are fun they are lower power and generate a lot of heat and the tubes wear out. I went to a lot of trouble to set up a double blind ABX level matched test between a Dynaco ST 70 and a Neurochrome Mod 86 amp and could not tell them apart ... I would highly recomend you try this yourself as it will really open your eyes and set you free from a lot of BS surrounding the hobby.
Which is funny, because I take that as the ST70 is just as good as the Mod 86
and a lot more fun to build. Granted I did the LM3886DR but still the SE tube amp was much more fun to build and not that much more expensive. It is all perspective. And while I never did a blind ABX test between the two I found myself turning the LM3886DR off after a couple minutes of listening and moving on to other things rather than sitting back and enjoying it. After a couple months of that I dismantled it and moved on. Is my tendency to sit and listen to the tube amp based on some psychological preconception I have about the sound? Could be. All I know is I enjoy listening when it is on so that is what I use.
Who knows, maybe a substandard power supply was hurting the LM3886DR performance the same way poorly done tube amps hurt their reputation.
I love tube amps but if someone said "here's $2000 to spend on a prebuilt amp" I have to admit I wouldn't buy a tube amp with it. But as something I can build from a schematic then a tube amp with point to point wiring would be way more fun for me. And tubes tend to be forgiving if you make a mistake during the build, transistors... not so much.
.... since what ultimately matters is the enjoyment the listener gets.
well said!