Ok so I've read up to page 155 or so of the thread and I just now got my unit. First I'll say for Senn HD 650's 0 gain isn't enough, only by slightly but having to have it 100 vol on the knob I boosted it up to 10db. Loudness is fine there really.
So my first thoughts, I'd been using Purity Sound that supports 600 ohm from Asus onboard amp from motherboard. Anyway With stock tube, I felt well not really that much difference really is what I'd been listening to for the last few weeks. Having warmed up only an hour or so. Yes I'm using usb foobar wasi etc etc . So really I felt I really honestly hadn't gained much if anything.
BUT then I changed to one of the orange globe I got from ebay. Almost instantly even with very short warm up time the highs came alive in a way I've never heard before ever from any device. I'm not sitting here with my mouth wide open in shock but man yea it's very pleasing indeed.
I have another orange globe to test and a bugle boy too so looking forward.
Listening to Fleetwood Mac's Never going back again 24 bit 96 and man that guitar is just singing, literally.
I'll add I can also see how some people can't hear it. To some people music is just noise I think, like having a tv on in the background when doing stuff. For the price I paid it's a steal of improvement really. Now to resist turning into Coil and Salvatore and becoming a tube hording mad man.