How's this working out for you? I'm working through (in my head...) the easiest way for me to deal with a lot of media and streaming, etc. My primary computer is always on, and I was contemplating storing it's iTunes library on a Synology NAS, which would let me manage the library like normal, but have a ton of storage available to it. And if I always leave iTunes on my main Mac open, then any AppleTV in the house can stream from it.
This is how I do it and it works fine for me. I actually have a windows xp box running iTunes and Audiogalaxy with the library pointing to my NAS box.
No complaints other than having to have the computer run iTunes. I don't have a Synology, I have a QNAP and I did not like the iTunes functionality on it. I may give it another try but it was a hassle to do.