I'm on the same boat. I don't see what the big deal is with the he500. To me, they seem well-rounded, a good headphone overall but it doesn't amaze or wow me.
Going up the grado ladder, the GS-1000i seems a bit too airy and thin. And the PS-1000 isn't worth it for what it sounds like.
I simply can't get enough or let go of my RS1-i. They really fit the bill for what I listen to - metal, classic rock, classical.
I'm eyeing the hd800s as my next upgrade though after a few more auditions.