I would like to add the hfi 580 to the table. Extremely durable, for me although they aren't THAT uncomfortable they make my ears sweat alot by around 2-3 hours. I got mine for 120$, but the price went back up a few days after. If you are willing to wait for the price to go back down the SQ will blow away the xb500's, with both the treble and the bass, atleast in terms of quality.
The xb500 is insane when it comes to bass. The bass is definetly what you hear, as it kinda overshadows the rest of the spectrum. Un eq'ed, it will perform very well on electronic and dubstep. My only warning is that it will be VERY hard to find headphones with that wont sound weak compared to it, without going up into 300$+ headphones.
+1 to getting the xb500's asap, they are being discontinued and the price is simply gonna go up.