And if, as one person wrote, we can't trust the frequency graphs to tell us what sounds flat, how do we even know if the studio monitors are flat?
If someone else started another thread with the subject "HD600 in the Studio" and went on about the virtues of mixing and mastering on the HD600, I wouldn't expect the response to look much different. Just replace "plasticy" with "veiled" and "weak bass" with "over-emphasized bass."
That was the point I was trying and failing to make -- these discussions have a bad habit of generating more heat than light, but ultimately, there's not necessarily a single right answer. It's the reason for all the "heat" that confuses me.