The kV rms varies greatly with the quality of the power supplied to the input of the transformer and even more with the form of rectification.
What is "quality of power"? Do you mean amount?
Is "form of rectification" - full wave or half wave?
Since the degree of rectification varies so greatly with various audio technologies from tubes to op amps to class D, maybe RMS is at least as meaningful as peak.
What is "degree of rectification" and how is it related to op-amps or class of the amplifier? RMS of power does not represent anything useful. Your kVrms * mArms is just power.
...or maybe radiography and audio have nothing in common and I’m full of s#!t.
You’re not. Asking questions is important.