I am not big on buying into Output Tubes, but have bought into such Tube Types recently as a result of having to.
I am with the Camp that believes the end of the signal being the betterment over what comes before is getting the wrong end of the stick.
The Sent Signal is everything, do ones best that they know how to, with the intent to provide what is to be met downstream the very best that is available within a constraint of a budget.
Small Input Tubes and Output Tunes in advance of any Power Amp Output Tube is where to focus the available funds. Only concern oneself about the Power Outputs when they are losing their MoJo and moved nearer the non-ideal spec's for the Valves.
Then if one wants to dent their coffer, why not money is needing to be spent, so why not on something that costs more, but comes with the notion, it is to be quite special. Hopefully all the other choices made, bring the true symbiotic relationship between the overall selection of Valves.