A few threads up, I had shared my gear that I'm currently using to power my K612 Pros as well as the DAC I'm using. As noted, the combo seemed to have good higher neutral level for the highs. If I had the oDAC back in this combo, it would have been a bit less detailed on the upper end. Also, I've owned the Asgard 1 before as well as the Asgard 2. I've found for some reason, I like the sound signature that the Asgard 1 provides. The Asgard 2, to my ears, sounded like a very neutral amp and Schiit did very good with that offering. However, the Asgard 1 seemed to have a bit more of the body of the sound filled out a slight bit more. I've also had the discussion with another member who had both, and we were essentially in agreement.
Finally, while I've never really been a fan of powering any headphones off of my iPod classic. On a whim, I used it for a few hours this past week with the K612. They performed very well and the classic could give 'em enough juice. Also, the sound signature wasn't dark, but had even a slight more lift to the sound than my desktop combo.
Enjoy the Music!