I favor 6f8g tubes not for air but for fuller sound.
@shkong78 , I just recently acquired the good fortune to have a few pairs to play with in the balanced input sockets of my SLP05. I am currently playing with a pair of National Unions and I was immediately grabbed by them. But now the jury is back to being out. I also had the good fortune of getting a pair of '52 Sylvania "Bad Boys" to roll in those slots, and I am not sure which I like best.