I would not pair HD700 and iFi iCAN at all... I was myself doing a research and iFi iCAN is suitable rather for HD600 or HD650, especially if considering to use iCAN's crossfeed.
HD700 exhibit serious ringing and peaks and its treble response is therefore problematic (a lot more than what some people find problematic about HD800), therefore I would most probably only pair HD700 with a tube amp... Well, I would never purchase HD700 to be honest, it's an overpriced headphone for sure. Get HD600, or go straight for HD800.
Edited by RustA - 5/18/13 at 9:48am