I'm on the verge of buying the ER4P/S. I listen to lots of classical, from strings to symphonies. And like many of us who listen to classical, also listen to lots of jazz and a little rock/alternative. The ER4P is great with classical, especially strings and quartets. I'm looking for a second earphone that would be fantastic with jazz, great with alternative and handle woman's vocals on new age/world stuff.
I've owned the EX600 so that seems like potentially a good fit. It does jazz really well.
I'm tempted to try the RE262, especially since I'll already be amping the ER4S. I like mids a lot. My single favorite earphone probably has to be the Se535 for the mids, though its not as comfortable as I'd like.
The GR07 seems interesting but perhaps covering a little of the same ground as the ER4P/S as far as being a more neutral sound, though the ER4P/S appears to have either better/more treble, depending on your taste.
Really interested in hearing from those who've heard more than one!