Homegrove …here we go again with this ‘warm’ business 😆. I had a valve mixer for a few years, they do get very warm (I mean literally… to the touch), but apart from that I think you’d struggle to hear any real harmonic distortion to the extent that it would be noticeable, especially on a domestic system.
If you really want a more tuned, harmonically pleasing sound, far better to flog the powered studio monitors and buy a good quality amp and some nice hi-fi speakers, like B&W or vintage JBL’s or Klipsch. I’ve always said I don’t understand the prevalence of studio monitors in home DJ set-ups… this is why I love the Mastersounds Clarity system concept, I had that idea first… those fuckers nicked it!
In the club scenario you describe I can definitely imagine this being the case… have witnessed similar myself. Did a boat party with the Sumsonic boys years ago, we tried 3 different Pioneer mixers on the system, and ended up using a Xone:32 (the little one) purely on the basis of sound quality.