If I had a 59RI, I would be contacting Ted Weber for a coppercap rectifier
module. He can supply one that will lower the working voltage of the amp
and still have the "sag" characteristics of your favorite rectifier tube.
Only then can you really go by what came in an original 59, because the
voltages are too high in the RI, which changes everything. You must have
the bias set correctly as well. I would also change the coupling caps to
Mallory 150s or the vintage ones Sonny JR is offering and change the plate
resistors to carbon comps.
This still won't make it the same as a real one, but it will be lots
better than it was, and doesn't cost a lot
Harp content: A good amp will inspire you, reproducing and enhancing
what you're playing (if you have good chops). If you're inspired, you'll
play better, if you're frustrated with tube swapping you won't. I think a
lot of the amp/gear obsession comes from amps not letting tone through, so
the corollary to Bob's motto is, accoustic tone is a must-have, but I
don't want to lose any of it playing through a crap amp, I want people to
hear what I really sound like.
Just my .02
kcmojo