For $400, you could go for the very well liked Denons. You could also get some Fostex's and a Thunderpants kit: http://home.comcast.net/~garybutcher/Thunderpants_TP1/Kits.html
Well I don't know any indestructible Denon headphones which has detachable cord and made off metal like V-moda or rubber and good plastic like tma-1 under 400$. Also all Denon models that I saw didn't look comfortable and portable.
Edited by Lawgun - 8/16/12 at 2:45pm