Mitch,
Definitely NOS only, nothing newer is even close…..70s & 80s, can be very very good, 50s and 60s can be magical…..though with some tubes dating can be difficult.
I’ll find my notes and repost in next couple of days. I went through a manic phase and have tested at least 30 types (I think I still have 40+ pairs?), I also I had an amazingly thorough link I’ll try to find if I can