As a rule of thumb I figure you need at least the cost of the HD800 on the rest of your chain to start to make it worthwhile. I mean look at the balanced HD600 that were there. I would say that easily sounded as good as the HD800 through the Anedio D2 headphone output. The only thing you may be getting is slightly more low level resolution and a little bigger soundstage.
Yes, that was eye opening!
Great sound by spending real big on the amp and the DAC and not spending a massive pile of cash on the headphones.
Makes me want to see what happens if I upgrade my DAC and maybe my amp.