After a little bit of searching, it seems nobody offers cable extensions for balanced headphones. You offer high quality single-ended cable extensions, but not double-ended. I realize one can easily just get 2 three-pin XLR male-to-female cables very cheap from just about anywhere, but this is kind of a tacky workaround, and I bet many people who are doing the whole balanced thing would pay an extra couple hundred or so for high audio quality. Just a thought...
__________________
Lossless --> foobar2000 --> SigmaTel Optical out --> HeadRoom Balanced Home Amp with Max Balanced DAC --> HD650 with HeadRoom's Balanced stock cable