I would have said the HE400 since I have yet to hear any genre this headphone can't handle but as the AD900X breaks in some more, I would have to give the nod to them. At first, classical music and vocals from a few opera tunes I played sounded stunning. Now the bass has become fuller so I am throwing electronic music at it I am enjoying it immensely as well. It just sounds so open and lively. I would consider the HE400 dark compared to these. I won't even add the HE500 to the equation since I prefer the HE400's over them. Sorry to add to the hype but after hearing these, the FXZ series won't get too much head time from me.
And here i was had my heart set on those FXZs but now i don't even know anymore. Great stuff Danny keep them "hypes" i mean impressions coming, really diggin' them.
Edited by sfwalcer - 1/20/13 at 1:50pm