[mandrake50]

  Great comparison... I've also owned both the HE-500's and 400i's and the only thing I would add is that the HE-500's bass definitely extends further than the 400i's. Bass extension would probably be my biggest complaint with the 400i.

I have not found that it is really a matter of extension, but more of balance. When there is substantial low bass in a recording, the 400i can produce it quite well.