And yes, there's no reason why you couldnt use an adapter to plug the headphone output into the Vali, but a better option would be to use the 2-channel analog output on the rear of the player.
Edited by palmfish - 12/26/13 at 8:39am
"7.1channel virtual headphone output
7.1channel virtual headphone output provides the ultimate personal entertainment experience, allowing you to enjoy your favorite Blu-ray Disc movie, DVD or CD through standard headphones with amazing 7.1 channel virtual surround sound.
The HD598 have a warm and forward mids. May be slow at picking up details but it sound excellent with classical, Jazz and it does female vocals surprisingly good IMO
I've recently gotten mine, but my initial impressions are it does classical (and in general instrumental) music very well. Vocals sound great, and the little bit of metal I've tried them with was handled quite well.
In general they seem to be fairly neutral, but still a bit mid/vocal centric (which I like). I don't find them fatiguing, but they are probably not as laid back as other Senns (just making an assumption from what I hear in these, and what I've read about others).
They seem like great all rounders, so I'm sure they will handle those genres just fine unless there is a particular sound you are looking for.
I recently got the Aune T1 DAC/amp with the upgraded 6922 tube and I love how it pairs with the HD598. I was just using a Xonar DG, which sounds fine, but the T1 is a noticeable imrpovement in sound quality. I'd compare it to looking through a dirty window, you can still see through it and it doesnt really bother you until you see it cleaned. Then you can never go back. Maybe the DG stands for Dirty Glass. The Aune T1 is the Windex.