I agree with MuppetFace the HD800 has a very tight hard punch even on trance tracks well amped. Personally though I think the HD 800 sound incredible even on the Fiio X3. Not super heavy bass like TH900 or Sig DJ though. Personally I felt that the k812 was a bit beefier. k812 a tad harsher up top, tube can smooth if that your thing. k812 > t1 is the feeling though
id post more but im using on screen keyboard with mouse
dislaimer is that i'm objective amps/dacs/cable wise.