Out of all of these, the only one I haven't heard is the E10. So now:
I currently use a FiiO E11 to drive my Sennheiser HD558. I'm looking in the market for a USB DAC, and am currently stuck between the Nuforce Icon UDAC2, FiiO E10, E07K, and the E17. I think I'm leaning more toward the Nuforce or the E07K... So after spending way too much time reading reviews this morning, I'm just straight-up asking. What do yall have to say?