Got a good chance to compare the HE560 to my own HD600 today. Level matched but on different amps.
I found that the HE560 still had a bit of that treble tizz that gets to me when listening at high levels. Not too different from what I remember the HE500 actually. In direct comparison, the HD600 had a much softer treble texture while maintaining equal (if not better/cleaner) attack. I would speculate that the HE560 does show to have a minor treble spike somewhere. Was ultimately hoping it might be more controlled and refined in the treble though.
Most of us agreed that the HE560 was superior at reproducing bass. On first listen, I actually didn't think it was significantly better. But part of it might be me preferring dynamic bass to ortho bass.
Regardless, I agree that the HE560 is an excellent headphone. Quite neutral and open-sounding which suits my two biggest priorities. But probably not good enough to pull me away from an eventual HD800 upgrade.