Depends on the NAS most have embedded server software.. some works well (netgear) some doesn't.. so first just try it with the NAS. If it's wonky then you need to run eLyric server on your Mac. Don't forget you need to download eLyric iDevice controller from the Apple Store to control it all. Also no need for an mp3 copy, you can set iTunes to export to your iDevice a 128k acc file.. Simply setup your Mac to look for the Nas as the iTunes library.. But remember iTunes does not play nice with Flac, Alac or Aiff.. Songbird does flac and it can export mp3
PS Audio PWD opinions
Setting up PWD this weekend to stream from my NAS via the bridge. I would appreciate any input on software likes/dislikes. Currently using mac and planning on loading with elyric/FLAC. However, I would also like to keep an mp3 version of my tunes in itunes for ipod? Can it be done?