"I generally listen to low rez downloads from Itunes or Emusic. I use a Macbook equipped with Pure Music, and an M2tech hiface Evo going to my DAC. I love the convenience of the Macbook and the Itunes interface. For this type of source material, would there be any real sonic advantage to switching over to a server and retiring the Macbook?"
I'm going to disagree and say no, there wouldn't be a sonic advantage and you shouldn't bother. You don't mention your specific DAC or speakers, or whether you are in an optimal listening position when playing music or just listening in the background, but still, with MP3 quality downloads I think you'd be hard-pressed to tell the difference between your Macbook and a dedicated server.
I'm going to disagree and say no, there wouldn't be a sonic advantage and you shouldn't bother. You don't mention your specific DAC or speakers, or whether you are in an optimal listening position when playing music or just listening in the background, but still, with MP3 quality downloads I think you'd be hard-pressed to tell the difference between your Macbook and a dedicated server.