You can't really go wrong with either the HE-400 or the HD600 for the genres you listed (I owned both recently). They have different overall presentations (the HD600 is more relaxed while the HE-400 is more energetic). The HD600 has a more balanced sound, whereas the HE-400 has treble peaks and a very noticeable upper midrange dip. I felt that the HE-400 easily had a bigger soundstage, though this may be due to the fact that it tends to make sounds seem distant. The HE-400 also easily had better bass (the best I have ever heard). However, it is worth thinking about comfort. Do you plan on wearing them for long sessions? The weight and clamping force of the HE-400 make them far less comfortable than the HD600. Ultimately, it comes down to personal preference.
this is pretty accurate. you really can't go wrong with either. there are fans of both headphones that will strongly push one over the other bc of their own personal preferences.
I have a he-400 and I personally love it! got used to the weight after a day and can easily wear em for 8 hr+ while i'm studying. i haven't really noticed a "treble peak and midrange dip" detracting from my music, though that is accurate depiction of the sound frequency curve. basically, OMG the bass is simply sublime. incredibly deep extension, very visceral feel, extremely tight and clear notes. I am in love =D heh!
for electronic, trance, dubstep, house, edm, hip hop, rap... the he-400 is a beast among critters!! works fine for other genres from my experience. perhaps the hd600 may be more technically flat or whatever, but my he-400 makes me wanna dance all day and my ears love em
it's a personal preference.
I too would highly suggest trying both before you buy, but if you can't, just go with your gut and buy from a place with a great return policy. heh! good luck with your search and I hope you find what you like.
note: actually, the descriptions online for both these headphones on this thread appear to be mostly pretty accurate. the problem is translating the description of how it really sounds into whether it matches your preferences cannot happen until you personally compare em yourself. everyone has different tastes! a lot of things make a lot of sense and sounded great in writing, but are not what you are expecting or prefer when you finally get to hear them. people can describe any pair of headphones accurately in a positive or negative way depending on their preferences.