well pretty sure I've made my decision ............................M50's back in the box back to guitar center :-(.......it was tough but for me it boiled down to a couple of small reasons:
1. comfort: 580's had a deep can, it wasn't that firm of a grip on my head also
2. leakage: 580's win! i mainly listen at a low- mid volume but sometimes i want to crank it up and i noticed that the m50's leak a little more than the 580's
3. sound: that was tough....honestly sound the same BUT m50's had harsher highs "to me". the bass seemed about the same.
Between a friend/ coworker and myself, we both found it tough to decide. Its not that much difference but no means just like all the other m50's vs. 580 threads out there. all boils down to preference.
let me put this in the mix....IF you cant get the M50's down in price nearest the HFI-580's or lower......hands down go to amazon and buy the 580's at $127. don't look back, think what if, blah blah......... you'll just stress yourself like i did. in that price bracket, you cant go wrong! And just think about a week ago, I'll admit that i was going to spend $300 on some Beats. I now have the 580's and Sony V6's for $200 which leaves me with extra to think about buying a portable amp for play from my laptop, touch pad,ipod or droid phone! i hope this little, I'm not that big of an audiophile like some of these people are review helps you out!
Would like to tell you supbrowawawa, Thanks also because if it weren't for your post, i would have been content with the M50's!!!