KR PX25 is best in most setups for me. I now have RK Px25 and will try that soon.
RK 300B was not great in GG, better in Pac.
Do you remember what tube you liked most in the Big 7? The Big 7 has changed a lot over time so it may no longer be relevant to my MKII but I am still curious.
So far I prefer the Tak 300Bs the most.