The E7 is FiiO's latest addition to their line of portable amps. The E7 also serves as a DAC, not to mention that it is the first amp ever to have a dual color OLED screen.
The E7 is quite the solid amp, and the casing is sturdy and metallic. It's case actually feels hard and uncrushable. The volume controls are firmly installed and not much of a wobble exists.
It was a little thicker than I expected it to be, though its light weight makes up for that. The source line in and USB input are on the bottom, headphone outs (x2) are on the top. The OLED screen is decent and glossy looking. The E7's GUI is good enough to serve it's amplifier purposes -- with keylocking, sleep timer, and other settings.
The gear I used consisted mainly of my Sony Walkman DAP, the E7, and Sennheiser HD 580 300 ohm headphones. The HD 580s after being amped immediately had more "presence" to it. The bass became more controlled and tighter. Soundstage seemed to have widened. A special note I have to say about the E7s is that they do not hiss. My Sony's produce hiss between songs, but the E7 neutralizes them. E7 is generally on the analytical side; without its bass boost*, the sound is natural and flat with emphasis on the highs. I preferred the bass boost on though. Additional listening shows that they are colorful and smooth-sounding.
The bass boost feature worked better than I expected and by far outperforms the flabby "clear bass" on my Walkman. There are three levels of bass, and none of them bloats the bass much, if at all. I tended to use the E7 with bass boost on all of the time, thus giving the E7 its areas of strength: the lows and the lower mids. The highs were less pronounced when bass boost is on, though it did not affect the overall sound quality much.
One thing I have to mention is that I had to push the volume on the E7 to its max at 60 for the HD 580s, and even then I sometimes felt that the HD 580s needed a little more. Still, the HD 580s had much more presence than when it was unamped, impressive for 300 ohm headphones. The E7 does well with instrumental music and sparkly pop music.
Sony MDR EX082 IEMs do not need amping, but the E7 made the Sony's sound fuller also -- the SQ of the Sony's were much more enjoyable. It's lows and lower mids likely rivaled or surpassed that of the Shure SCL4s from what I can remember.
E7's DAC functions supersedes its amp functions. The DAC sound to a degree resembled the sound of my full size stereo speakers. The bass boost became more unnecessary.
If you are looking for an amp/DAC combo, the E7 could be right for you. If you like an analytical sound and emphasis on the lower spectrum, E7 is the one. Finally, the E7 is well suited for IEMs and you can't go wrong with them for the price.