I finally got the S500 today.
One thing I noticed is that on bass heavy tracks, the headphones vibrate alot. And the bass is all over the place. Sounds very muddy/muffled.
Perhaps my the Bass EQ on the Poweramp app is a bit too high but, none of my IEM's seem to have issues with the Bass settings.
look few posts up for the cork mod. Much more controlled bass after the mod