Well, I received my HE-400s on Friday and have given them a good few hours listening, with about 5-10 burn-in on top and I am disappointed. Yes, they have clout in the bass and have a vivid overall presentation of music, but the mids are boxy and honky, with the highs tarnished by something in the very upper ranges being exaggerated.
This leads to a totally unrealistic presentation of timbres of strings, brass and other orchestral instruments. They sound like they are totally EQ'd. I'm pretty gutted at the moment, as spending this sort of money and reading such great reviews, I expected much more from them.
These conclusions are coming from running them through a variety of setups, including an Arcam Alpha 8 integrated amp, my Asus Xonar Essence STX soundcard and a Fiio E11. I am using the velours too, which did improve the sound greatly from being quite a dull and muddy mess at first. These headphones are in serious need of opening up in the upper mid/treble department. I can see why any fans of electronically produced or manipulated music might love these, as a realistic recreation of timbre is not relevant. For anything acoustic or using live instruments though, I'm disappointed. I mean, even listening to spoken voices, one can hear the colouration affecting the whole range of frequencies. I do hope these start to grow on me and that I'm maybe just too used to the generally brighter signatures of my other headphones