I was going to say I don't think the HD-600 are all that neutral sounding (but close), but that would only derail this thread and make people hate me.
I forget this is the HD-600 appreciation thread.
I actually think the 580 sounds more neutral (same driver and all)
Different grill, and the hd600 has tighter driver specs.
If the hd580 sounds more neutral, I'd imagine it's only marginally so.
but yeah, there is no debate... the hd600 is neutral.