HEX v2 with some mods vs HE-500 with more.
Hex's are cohesive, lack top end air, go low in the bass, but don't move lots of air. Lack a bit of definition in the mids and highs. Easy to listen to, makes everything easy on the air. Lack body, more headphone like than the the HE-500.
HE-500 don't go as deep in the bass, but move more air, more tactile; mids are liquid, have a good degree of body, creamy and real. Highs are expressive but not hard, cymbal decay still too long but mods cut it way down. Wider and deeper soundstage then the HEX v2, HEX a bit taller. HE-500's are a bit slower, HEX v2's faster and impose less personality, but toe tappin' is a lot less frequent.
My #1 and #2 cans.