Well, I took about 10 hours or so with the E10 yesterday before concluding that. The E10 compared to my MBP's output sounds more congested, less open, and high frequencies are not as extending. It sounded a tad on the warm side and it's a bit muddy, which... is definitely not my type of sound. I like open, clean, and crystal clear. Basically treble-oriented rather than bass.
The Fiio E11 adds a tad of warmth by itself, but I find the E10 adds even more, so it sounded very congested to me. If I wanted that sound signature, I always have my Dr. Dre Beats Solo to do it.
But then, it may just be my M50, and I admit... the MBP is the only output that my M50 seems to "shine" with. Even with a Cirrus Logic DAC in my iPhone 4, iPod Touch 4 and iPad 2, it didn't really "sing". I guess it's just a synergy issue.
I'll have a DT990 Pro 250Ohm in next week to test. Perhaps that one would pair better.