@mozartfan, This is quite the post. I have bought dozens and dozens and dozens of both Russian and Chinese made power tubes (mostly KT88s, but also many others). China has come a long way in their power tube reliability issues of previous years. Today's Chinese made tubes are much better than those of 5-10 + years ago. Would still say the Russians are better for long term reliability. Have had to replace fewer of them in my amps over months of use.
As for sonic qualities, the best sounding most organic output tube is the Shuguang Western electric Plus series (WEKT88; same series available in 6CA7. 300B, 845,. etc); This tube family blows everything else into the weeds sonically.
But the reliability on these shuguang tubes is not as good as the Russian made tubes (GL KT88 for example). So if you are going to run Chinese tubes, need to stock up on lots of spares, but you will get a nice sonic improvement by doing so.
The Shuguang factory is in the process of moving so only real option for chinese tubes today is PSVANE, which are also good. Check out their KT88 gray glass tubes.
From the Russian side, the GL KT8s are my favorite. do not sound as natural as the Chinese Shuguang WE varieties but are more reliable, and last longer.
For input tubes, really hard to be the PSVANE T-II 12A_7 series. They are reliable and sound exceptionally good.
for 6SN7 types, the Shuguang WE variety tops all, even NOS types.
best
