The iGrados are flatter, less presentation to the instuments. I prefer the 60's except they are not as handy to walk around with the portable. I need to try the mods that have been suggested for the iGrados. Didn't end up liking them as much as I thought I would. I love Grados and own the 60's and the 225's. PX100s are better except a little light on bass. Koss Portapros are the best in my opinion for portable use.
I do have the iGrados (not the SR-60s...which is why I asked the question) and I modded them. I removed the foam between the driver and the chrome screen. To me, this mod greatly improved the sound but at the cost of isolation. It brought out the highs and increased the stage.
I'll have to try removing the foam. I played with the chrome covers a bit one day but they didn't seem to be wanting to come off very easily. I think they would sound better if they opened up a bit more.