This is the thread that convinced me to purchase the QX 5 unheard, while I cant chime in on the different dac,s being currently discussed I can chime in on the optical ethernet vs straight ethernet or USB and yes the optical ethernet gives a much better portrait of the music in dynamics, soundstage, detail and air. I with back and fourth lately between USB and optic for the fact Im burning in a new preamp and its running 24/7 so during the night time I switch to the USB and when I switch back to the optical ethernet thier is a clear difference in those areas especially transparency. There is also a difference in volume levels between the two in my set up with the ethernet being a few db louder.
I feel the difference in straight ethernet vs optical is in the midrange on up, a tad more transparency and natural timber, bass is fantastic in both.