I think these are bit overpriced for about 100-200$.
The sound quality is similar to HD 600/650, I would say more closer to HD 600. ANV has a bit of grain in the sound like just like HD 600 = less pixels. HD 650 are a bit smoother/hifi = more pixels.
HD650 are more darker, but I would say the ANV is a quite dark headphone too. Definitely air missing = rolled off.
ANV and HD 600 both quite neutral, which is nice.
ANV has a bigger soundstage than HD 650. HD 650 sounds a bit "mono" after the ANV.
I would say nice comfort, but Senns win here in my opinion. HD 600/650 are one of the most comfortable phones out there. ANV tends to move a bit on the head and the sound changes because of that. ANV is a bit sweatier too than Senns.
Nice cans, but overpriced. Should be around 299$.
From memory HE-500 definitely beats the ANV by a mile and HE-500 beats the HE-400 by a mile.