Neutral is definately the way to go with both headphones, but anything brighter than that I wouldn't pair with the hifimans.
The problem is that many many people feel the neutrality is nearer with HE500 than with LCD-2 rev2 and/or pair their phones with non-neutral amps and then judge their signatures. They even feel HE500 is "darker than ideal". It's simply not true if you are talking about real neutrality (flat FR graph is not equal neutrality in the world of headphones).
LCD-2 rev2 are for sure a bit more neutral than HE-500... Ideal bass, ideal mids and slightly recessed treble in specific regions (not completely). HE-500 are not completely flat to the lowest regions, mids are going to be about the same and the treble is peaky from 7 - 11 khz ( = around 10 khz). But this can work better for many people - that's absolutely ok. But remember that treble is very easy to EQ, bass absolutely not.
Edited by MHOE - 11/16/12 at 1:33pm