I have a BeyerDynamic T50P and a Sennheiser HD598, both work fine with E17. That is to say, I can hear "more" via E17 compared to a direct connection to my PC. The width and depth are much improved, and optimization is remarkable. Frankly, at that price, I can say that it's a good surprise.
The DAC part is correct, I have not had the means to test with the music of 96/24, but already with 44/16 files, the result is already impressive. I'd like to test the 192/24 mode with an optical fiber, but good for the time, I did not means ...
When connecting to E17 MP3 player (mine is iAudio i9), it only becomes a headset amplifiers. My personal opinion, it is not an amp "powerful", but more than adequate for an HD598 (60 Ohm).
In short, this is a great product with a very good price / quality ratio. For those who want to start their lives HIFI with a fairly limited budget, E17 is a very good choice to help you open the door HIFI music. Good luck!
PS: I also tested E07K My friend, I found that E17 is better, better DAC + more powerful amplifiers. For me, the only highlight of E07K compared to E17, is autonomy ... (and the price: D)