As much as I loved my AF2 (spent 9 whole years with it) and now my AF3, swapping tubes on these devices was never satisfactory for me as I had a real world experience with tube swapping on my Super Lead.
I would much prefer if the transconductance was put in the sound/behaviour equation of yours at least maybe the results would be more realistic. But, hey, what do I know.
PS: with EL34s the differences were even more obvious when the volume was wide open, it was very easy to observe the differences in sound, behaviour, compression, how "controlled" the amp remains or not, how the bass frequencies were behaving or if they were all over the place etc. Going from any EL34 quad to a 6550 was night and day accross all volumes, frequently-wise, gain-wise etc. That's my experience.