Well, FWIW, I've been very happy with a quad of Psvane 6BQ5 & 12AT7 (Tubelab SimplePP in pentode) and pair of Shuguang Treasure 6CA7 ( custom Eddie Vaughn SET)
Not inexpensive, but in both cases transformed the amps - both in terms of dynamics ( & grunt in the case of the P/P) but also finesse and low level detail & resolution.
I don't currently operate anything requiring 12AX7s, so I can't comment on the Psvane version, but I think it's got a lot of good reviews as well.
8 of any type of zoomy power tubes for this amp will cost money, but you were prepared for that going in, right?
