First, I agree with you that there is no logical difference between proprietary media servers like the N-01 and generic computers with music player software installed. Their advantages are silent operation, preinstalled software and a user interface similar to that of other audio hardware. One can, of course, modify standard computers to do all this with a little effort.
Second, the outputs of the N-01 are stereo analog outputs, XLR or RCA.
Third, the advantage of using external storage media connected via ethernet (wired or wifi) is the ability to relegate noise spinning discs to another room remote from the listening room.