Interesting reply, thank you. Along with incredible knowledge about tubes, you also must have incredible hearing sensitivity. You conveyed you listen to your music very loud I hope you are appreciative of the likelihood the sensitivity will diminish rather quickly overtime. Or maybe not.
I guess since I'm using an MC 901 amplifier, changing the smaller tubes made sense, but because the solid state section of amplifier focuses on 350 and below maybe new Power tubes to replace whatever the heck is used for the stock tubes which I think is JJ may not be that meaningful. However it appears they do impact upper frequencies in a meaningful way so probably Worth doing.
I keep in mind that there is considerable value in higher priced NOS tubes because presumably they will last a heck of a lot longer, sound a lot better and hopefully the quality will hold up better overtime.