I'm lookin into getting a Synology NAS, but I'm not too savvy on the features. In this situation, would the music still be available over a WAN? So in my case, all of my music is kept on my Macbook ...

Certain iPhone, iPod touch, and iPad users can now stream all manner of media from their iTunes libraries on a Mac or PC to their devices via Home Sharing. Ars has a quick how-to to get you all set up ...