I strongly disagree with Bill on this question, but we use wildly different amplification.
If you're just concerned about neutrality, here's a rank of my headphones (once again, the order here is just based upon neutrality):
1) HE-6
2) Mad Dogs with Alpha Pads
3) LCD-3
4) ESP-950
5) HD650
I use a Schiit Magni, Schiit Asgard, Decware Taboo, and Cavalli Liquid Glass for amplification. I do imagine that when under-powered, they may indeed be quite far from neutral.