I've tried running my Node2 through a handful of different external DACs using both coax and optical digital outputs using comparably priced cables. The difference in sound quality between coax and optical is marginal at best but different DACs do make a difference. In a couple of cases, I even found the analog RCA output from the Node2 sounding better than the digital output(s) through the DACs. I think the difference(s) you hear using an external DAC will ultimately depend on the quality/resolution of the rest of your "system" and in some cases the quality of the cabling, both digital and analog, used through the system.
Hope this helped.
Hope this helped.