Take the bias rite. Get mA reading. Take ohm meter. Measure plate voltage on power tube (connect positive end to pin #3, neg end to ground). (Some bias-Rites have the plate voltage switch - use that if you have that version) Multiply pV x mA. That will give you IPD of tube.
mA = 32
pV = 495
Multiply 495 X .032 = 15.84 watts of plate dissapation.
EL-34 MAX plate dissapation is 25 watts. Being that this is a fixed bias amp, you want to run this tube at 70% of plate dissapation = 17.5 watts MAX.
So, 15.84 watts of IPD per tube is acceptable. You want to bias to the tube pulling the most current.
Last time I biased a Shiva, it sounded real good at around 14 watts of plate dissipation. Use your ears and use the math and you will be OK.