Here is what I have and do, I know there are plenty of forums on here for this, but as my first, post, I figure I'd share my experience.
Mac mini to receiver via toslink on gives you stereo sound and most receivers with USB only accept 2-channels on the USB, so currently, because of a bug in quicktime, their is no way to get 5.1 through the toslink on a mac. I know on forums on the web (including this site) they outline steps to force it to work, it doesn't work properly, if you test the signal, you will never find all 5.1 channels of information. If you use a usb sound card with optical, then you can set it up and get true 5.1.
I use the mini directly hooked up to the tv, harmony remote, understudy plugin, pyetv plugin, it all works pretty well, and at least for my wife is wife friendly. The mini feeds the apple tv's in the rest of the house.
Enjoy, go for it. I have found in my experience it is better to have the content directly attached to the mini, than through an NAS.