Great post - I'm on the fence between this and the RME ADI-2: both are "transportable" for my needs, which is basically moving around the house, or to and from a known location, to a place where I'll be sitting and listening for a few hours. I'd be lying if I said I didn't love the nerd features of the RME (even if I don't use them) and the WA8 is obviously possibly doubt the price ... decisions, decisions ...
Anyway, I really appreciate all of the posts on uses and experience as it's helping make a decision. THanks to all!
I do love the WA8. It pairs wonderfully with the HD800s - for which, for my taste, a tubed amp was a "necessity"
I think the real valve, class A amplification is unbeatable and there's no other amp on the market offering this.
As use case scenarios go, I never consider audiophile listening on the go - really can't get that that with street, plane, train noise around - no matter the headphones or amplification. For that my iPhone & airpods or any decent noise cancelling HP are good enough.
My use case scenario for the WA8 is late night listening and in room listening while away. I got a case that fits nicely both the headhones and the WA8 in between and that's the best sound I can take with me anywhere.
Had the ifi iDSD Black Label for a while and honestly, sound through the WA8 is so much more satisfying - for my taste. For the price, the ifi is good (though I really really didn't like their DAC implementation) - but the amplification was good. At home, I do prefer to hook up the WA8 to my system DAC, but on the go I don't feel I'm really missing anything. As a player I just use my phone as a high resolution player, connected via USB to the WA8.
Never had a chance to listen to the ADI-2, however the WA8 i suspect has a different sound signature due to the tubes and that battery is really nice to have to move from one room to another without wires. Also that might help the sound and low with noise floor. Actually I never ever heard any noise at any volume with the WA8.
Hope you can test both and choose the one that suits your taste best!