Just wondering, what are you actually doing with the tube? I presume (and please, correct me if I am wrong), that you are taking the differential outputs of the ES9018 and converting to voltage with a pair of standard opamp transimpedance amplifiers, followed by a differentially connected opamp with sallen-key LPF, and then an optional tube emitter-follower buffer on the output or a 3rd opamp buffer stage, each of which with maybe one more filter pole?
I dunno, unless it is something extremely different than this, it would be much cheaper (and more interesting to most here I suspect) to just have a balanced LPF/buffer stage, and lose the tube and associated power supply completely. Heck, a DIO opamp LPF/buffer stage would be pretty cool, and give you the SE and differential outputs with no real addition in parts count. Meh, whatever, its your dac, you are free to do with it as you please.