With all due respect to the above posters, I would say that the HD-800 and TH-900 are equal in terms of quality and in what they bring to the table. Both headphones shine in certain areas. Being a new owner of both headphones as well as a veteran Sig Pro owner (if I can use that term ..lol)
I find myself reaching for the TH-900's quite a bit. I agree though that the HD-800 is a detail monster and possesses a Godly soundstage factor of 10, there is still something very organic, magical about the TH-900 (excuse the HF cliché terms)
Perhaps its a mood thing also. I would agree with Canadian411 that "an endgame" solution is to own both to a degree. While I wouldn't go as far as endgame it comes close. I would imagine for me a SR-009 / Abyss combo would be true endgame material.
Cheers though to the HD-800 for all that it does great. Oh forgot to mention, I feel that the TH-900 bests the D-7000 considerably....just my 2cents.
Make no mistake though, the HD-800 is a fantastic headphone that any Head Fi'er deserves at least to hear or better yet .... own.
Edited by Mortalcoil - 5/7/14 at 7:17pm