Ah, the perils of peer pressure... >10k is definitely elevated over the 4S, though, and IIRC SGS didn't like that (I find it tough to listen to bad tracks with it over time as well).
Also, less 2.5-3k emphasis than the 4S, but I don't think SGS would mind. What's most important --- less THD+N between 1-5k.
For the 4S, the CTM CT-100, CanalWorks CW-L01, CW-L05QD are the three CIEM models most like the ER4S to my ears (same/similar design principles). CustomArt Pro210 will probably sound like it too, but I haven't heard it.