I still think Shure SE530/535 have the best mids in universal IEMs, although I haven't tried RE262 amped (it doesn't sound as good as the Shures when unamped). e-Q7 also has really, really good mids as does the aforementioned RE262, even unamped. e-Q5 and FX700 also have beautiful mids. Actually, FX700 is the only IEM I tried that sometimes seemed to rival SE530/535 for mids quality. It's just that the midrange on this IEM is not as prominent as on the Shures and is a bit behind the bass and the treble. If you are looking for best balance with the best mids, I think e-Q7 may be the best option - it sounds great unamped and doesn't require a great fit to sound good. The Shures, although unparalleled in midrange reproduction fail to impress unfortunately, unless you can achieve a really good fit with them, which for me was next to impossible with universal tips. If you want a powerful, warm sound and like bass strong and punchy, the FX700 may be just what you are looking for although they don't isolate well, since they are an open back design. RE262 is probably only balanced sounding when amped, because unamped I found it severely lacking in the treble. e-Q5 may also be a good option if you want a neutral sound with a bit less overall detail than on the e-Q7, but better balance. Personally, for great mids I would go with the e-Q7 or FX700 though - the former for a more balanced sound, while the latter for a more V-shaped, fun sound. Actually, I think that technically FX700 is superior to e-Q7 overall - FX700 has a more refined treble, better soundstage and deeper bass, but if you really love your mids, then e-Q7 is really strong in that part of the frequency spectrum without sacrificing much in the lows and highs.
