Good news for usb DAC use on Rpi : the new Pi3 will have separate bus for the USB-ethernet and the Wifi LAN. The “pop” and “scratch” problems must be solved.
Unfortenately it does not help much when you cannot use wlan and have to use ethernet.
In that case, tests show that the PI3 still suffers from usb audio hick-ups when playing Hi-Res.
The Odroid C2 shouldn’t have the popping USB.
Gé you’ve tested the C2, can you confirm that the USB output is cleaner than with the Raspberry Pi’s?