Really happy to see all the on-topic replies here. Especially happy that this discussion has stayed focused on the union of tube and Class D as opposed to a free-for-all discussion about Class D vs whatever you like better.
Those discussions are already plentiful in A’gon.
I ask this question in part because I'm about to go fully active in my main system and wanted to know what kinds of combinations had great synergy, but also because I've always suspected that a juicy tube pre with a solid performing Class D would be heavenly.