I just received the HD650 and dislike the sound. I like the idea of vocal isolation and mid forwardness, but it was overdone here. The mids became a little too sharp and the background instruments too quiet. The technical side of things, like soundstage, imaging, microdynamics, dynamics, detail, resolution etc. were also of lower quality (in comparison to Focal Clear). I used SMSL Sanskrit 10th MK2, SMSL SP200 and Amir's EQ settings. If someone would like to upgrade their HD650, look no further than Focal Elegia with Dekoni Sheepskin Pads, which has the right amount of mid forwardness with greater technicalities.
EDIT: I see that a lot of people like the HD650 very much and dont experience the problems which I have experienced.
I can think of two possible reasons for this:
1. they never compared it with a higher end headphone. On the other hand, for example amir and solderude have tons of expensive headphones and did not experience my problems.
2. we just hear differently, because of different ears, brain, body etc.