If you're getting a sub $500 USB turntable, chances are it will sound worse than digital lossless files through the Bifrost.
But answering your question, I don't know honestly. USB turntables usually come with digitising softwares for needle drops and copying, not to listen through computer.
In the meantime try wrapping the tube in thick cloth to insulate the heat. It worked for me, and hot 6922 sounds sweeter but since they weren't made to go that hot it might kill the tube faster. Do it when you're very sure you're getting new tubes.
On paper reference sound gets thrown a lot but get a few TOTL reference setups be it head fi or hifi, they'd sound different to each other. So who determines which one is dead flat or accurate? 10 heads could give 10 answers.
When will we realise this reference sound is just us satisfying the reference dead flat sound signature in our own head?
As far as headphones go, they do sound somewhat real. I do think that if I were to spend that much for source+amp+gear, I'd spend it on a speaker setup instead. Felt a holographic speaker setup and I can't go back