Many moons ago I had a CJ premier 11 amp. It had Svetlana 6550's. The violet color plasma within the tubes would swirl around. It was memorizing. Alas, no Svetlana tubes being built any more....
I live in the Caribbean so I don't need any extra heat, thank you. I use Class-D amps partially to avoid the waste head. Cooling is just as expensive as heating and local power generation costs are ridiculous.
I get my tube "fix" via pre-amps. The tubes get "uncomfortably warm" as opposed to hot. I also opted for a pre that allows me to bypass the tubes or even go completely passive, if I'm in the mood for "ultra accuracy".