I want to elaborate..as briefly as I can.. on my above remarks.There are solid reasons why high powed valve amps have problems. The obvious one is the sheer unreliability of having to run many valves...as a generalisation, the more valves the more chance of failure.Anyone who uses Audio research stuff will learn this! Bigger output transformers are far harder to build well...and you might be surprised at how little even'high end' firms are willing to spend on them (ask a good technician.)
Then, we get the poor quality of the modern big pentodes...just compare an original gec kt88 to a recent Chinese or Russian one. Coarser sounding and less reliable (I know, I have been bitten by them). But most of all, try to actualy listen. Get efficient speakers, then compare valves, from the ultra low output stuff (Px25 triode), up through the 2a3, 300B, onto the el84, 5881, el34, then finally to modern kt88 and 6500 valves (often virtually the same valve.) Of course there are many variables in all this , but repeat the comparisdons over a number of years with different amps, ask other experienced valve users, most of all compare the sound within a range (say the Jadis 30, 80 and 200). Then compare with the best solid state amps.
At the end you might still like big pentodes (although I doubt it) . What you certainly won't be able to say, is that people who hold views like mine have no sensible case to make. Thank you.