Nice measurements. I LOVE the HD600.. the only reason I sold it was to help fund an HD800. After having the HD800, I still think the HD600 could harmoniously coexist with it. The HD600 is more forgiving, warmer, and is less picky with upstream gear. It has a midrange that's absolutely delicious. I feel like it had more midbass emphasis than the measurements indicate. That being said, this was the first phone (IEM or otherwise) that had a midbass boost (and rolled off lower bass) that I really liked.
I might prefer the comfort of the HD600 to the HD800, too. I liked the HD600's tighter, more decisive grip & more substantial headband padding to the HD800's very comfortable, albeit, slightly loose fit. I had an HD580 before the HD600.. and while they sounded awfully similar, I would gladly take the HD600 over the 580 due to the better build quality, looks (I dig the marble patterning), and tighter driver tolerances.