FWIW: While I am waiting for the new WE tubes (I hope), I can share with you, that I - while not being an audiophile - enjoy good sound quality. Please note, that this is of course my
very subjective opinion/experience. Will not try to lure you in the very deep rabbit hole of HPs
. However, before the Pro iDSD, I have had a couple of other DACs, but based on very good reviews, I went for the iDSD 2.5 years ago. Initially, I only used this (i.e. no external amp) with mainly Grado headphones. They are open HPs, very easy to drive and are very good with a lot of genres. Not so long ago, I got a very favorable offer and bought a 2nd hand Pro iCAN. Of course, they are meant for each other, but it allowed me also to try experimenting with the balanced out and I bough XLR cables for the HD650, Focal Stellia and Arya V2. I think dependent on the choice of headphones, you may find that an external amp will add to the listening experience. Powerwise, I think the iDSD will drive most HPs and now when you successfully have swapped tubes, I guess, there is lots of room for experimenting. It is really a nice DAC.