Received a balanced HD650 cable from Corpse Cable on eBay last night and finally gave it a listen...I can't believe how much better the HD6XX sound with this cable over single-ended. I recently upgraded my Schiit Vali 2 to a Jotenheim and am blown away by the additional detail and clarity this amp provides. The Modi Multibit continues to impress me so much. It's the best DAC I've ever heard and it's hard to believe the Gungnir Multibit (my next upgrade) is even more precise and detailed. NIN is especially wonderful to listen to with all of the little details and layers to discover. I can't believe how many new things I've heard since upgrading my audio game over the last year.