My Superlux HD661 arrived a few days ago!
I have to to say that at first impression i am a bit disappointed, probably because i'm not used to headphones.. First thing i notice is that music sounds quite distant (this could be a pro for someone, idk).
Sound quality is ok, sub bass lacks a bit but the sound signature is supposed to be neutral, and EQing can partially solve the problem.
The problem is that these sound like earbuds to me.. it's not easy to explain, i don't feel the clarity of an IEM. Since i own Vsonic GR99 and GR04, maybe i am used to a warm sound signature while these are more analytical..
BTW, i started the burn in process and probably i'm going to buy a portable amp, just to check the difference.
Anyway, the build quality is very good, they are beautiful, have a fancy package and nice accessories. Also, i don't find them uncomfortable at all and the isolation is great. I'll post my second impression in a few weeks!