If that is the case how can EL34 even be considered?I think we're going around in circles. A KT 88 runs 450volts 55-60mA very well. A kt 90 requires more than 450volt/80mA, which significantly reduces the distortion. A current adjustment is necessary otherwise you will be disappointed with the tubes. my opinion.
I would rather try first out a cheap eh kt90 to see if it works in the amplifier.