Just checking in after a couple more days with the HD800 and the Vali.
Still love the combo. I think it's great.
last night I added the Emotiva DC-1 into the equation. I didn't do much back and forth testing with the Burson 160D output as I was tired but I did notice a further slight increase in soundstage, and slight reduction in midbass heaviness. I can't really get into more detail than that without more listening time.
The DC-1 headphone out, by itself, can highlight the treble response in the HD800 and sibilant tracks can sound really sibilant. maybe it's more accurate, maybe it's exaggerated. no idea. I know that it's much more pleasant to listen to potentially sibilant tracks with the Vali hooked up tot he DC-1 line output.
don't get me wrong, it's not glossing over too much -- really excessive sibilance in a recording will still come through but it's not as sharp and disturbing as it is from the DC-1 headphone output. The Burson headphone out tends to blunt sibilance too, but this comes at the expense of reduced soundstage and a more blurry bottom end.