I've got a pair of david clark x11's that are a warranty replacement and are brand new unused in the box. My first set broke and I couldn't wait the 2 weeks to get a replacement, so I went ahead and bought another headset with the intention of selling the replacement. So here it is. Looking for around $600 shipped, but I'll take offers. These are brand new, so $600 is dirt cheap.
http://www.davidclark.com/X11/index.html