I just received the E11 yesterday. I am using it mostly with my Sony NWZ-A816 DAP and Fiio E5 LOD. I have a variety of different, great headphones now with different impedances and sound sigantures to test with the amp: Hifiman RE0, RE272, JVC FX700, Denon D2000, Shure SRH840 and Beyer DT800/600. So far, I have mixed impressions of the amp. I will post more later on, maybe in a separate thread, but for now I gotta say that I am not impressed with the treble, although the mids and bass sound very nice. The highs on the E11 strike me as somewhat attenuated, soft, perhaps a tad grainy and compressed. High frequency extension is fine, but with headphones that are especially revealing the high frequencies like the RE0 and DT880, the Fiio E11 sounds a tad weak up there. For treble, I actually prefer listening to even the DT880 600 Ohm straight out of my Sony's headphone jack or straight out of my Sansa Clip. The mids and bass are a different story though. The E11 seems to have rich, textured, well separated and generally highly resolving mid and low frequencies for the price. Certainly a good bit better than the built in amps on my consumer grade DAPs. Vocals sound powerful and all the emotions seem to be portrayed very well. Soundstage seems OK - quite 3 dimensional with a good sense of space, weight and good portrayal of spacial cues, but I think my Audigy 2 ZS with kxProject drivers wins in this regard - it provides better, cleaner stereo separation, whereas E11 sounds a tad congested by comparison. Actually, I think my Audigy 2 ZS with kxProject drivers sounds better than the E11. Not sure where that puts the E11, but I don't really care because I can't take my Audigy 2 ZS with me to listen on the go anyway. What matters is that E11 is a sizeable upgrade over regular, consumer grade DAPs, especially in the mids and lows. The highs are questionable to my ears, but at least they are clean, well separated and do carry a good amount of detail. The E11 is also powerful - VERY powerful. I almost killed my poor ears once when I turned the volume on the amp to high by accident when listening through my SRH840s. So be careful!