Hello, I've been using the Sennheiser HD555 for some years now and wanna buy some better one (really like them though). Recently I've tried the Hifiman HE-400 but didn't like it too much because it sounded too bright and "far away" for me. I've been reading these and other forums a lot the last weeks and now I'm basically deciding between the hd600 and the k712pro. I'm mostly listening to HipHop (Eminem), Vocal Music and some electro/pop.  I've got an Asus Xonar Essence soundcard. Do you have any recommendations? Should i go for the sennheisers cuz i was pleased with the 555s or are the k712s better?

Some notes on what you're considering on doing:
 
Headphone Choice. I haven't listened to the HE400, but just one small detail to consider: if you feel the HE400 are "far away" from you, note that the K712 might be "worse" (I personally would consider that a plus, as it would mean more like a speaker system and less like a typical headphone) in that regard. It has slightly thicker, but more importantly angled earpads (thicker towards the rear/behind the earlobes) designed to mimic speaker toe-in angles and reduce the strong L-C-R with recessed (image/location-wise) sound sources between L-C and C-R. The HD600 has less of that obviously; I can't make any guesses as to much more intimate or up-front it is vs the HE400, but in case it helps, here's a very rough, quickly done, simplistic, top-down diagram of how most recordings image with my reference system using the same headphone:
 
Triangle = vocals; rectangles = (electric) guitars, circles = percussion (cymbals at flank, oblong is bass drum)

I think 612pro might suit you well over hd600

thanks. are the mids the same for the 600 as they are for they 650, since ive read the 650s are pretty much the best at mids.
 
and how do the k712 pros compare to them at that?