For those with the HD800 and on a budget, I say get the Vali and with the $$$ saved, invest that into a top-class DAC. You will not be disappointed.
Or, a good DAC and some top-class source files. The HD800 forced me to (happily) discard about 10 years of mp3 music files. Sign up with Highresaudio.com, Hdtracks, Bluecoast, Linnrecords, e-onkyo, etc. Download their free samples, use their discount codes, download free so-called `needle drop` 24-bit rips from quality vinyl for music you already own, share music with your friends. I`ve built a new library of high-resolution music and it`s made the HD800s, my IEMs and my speakers huge sources of pleasure.
To appreciate the HD800, you have to move on from over-compressed, lossy files. The most expensive amps and dacs in the world won`t overcome the issue.