If anyone is looking for a low cost dongle DAC, I just got this Astell&Kern AK HC2 usb DAC. It has wonderful separation and superb pin point imaging.
The housing is made from Billet Aluminum and utilizes dual CS43198 chipsets for awesome spatial sound.
Supports 4.4mm Balanced Output
Powerful 4Vrms Output
this unit is a couple of years old and AK has a couple generation newer usb dongles, but this one is highly recommended.