I really liked the comparison here, and seems to be spoken of by other's who have done similar comparisons. Wanted to ask if you have ever listened to the K712 and or compared it with the HD650? I am able to trade for one and wanted tro hear some thoughts on it if you have. I would be pairing the K712 with the PanAm to give it a little bit of warmth. 

Never listened to K712. But currently I own the HD800 and it's a huge improvement over the HD650. I don't agree with reviewers who consider the HD800 an improved version of the K701.