I now use the E3 exclusively with both my MDR-NC60 and MDR-NC22 phones, to add the moderate power boost as well as much needed bass and tame the otherwise over-exaggerated treble.
As for a clip for the E5, later this afternoon, I will try adding a clip onto the back of my E3 (a mod job that just requires a little Krazy Glue or equivalent), the clip being from one of my old Sony MD/CD remotes (from a black Sony RM-MC33L that came with one of my D-NE700 PCDP, not needed as I have a color-matched RM-MC33EL to match my silver D-NE700), and I'll post pics of the finished product on both the FiiO-related topics.