I use a Windows Home Server box (
http://usingwindowshomeserver.com/2009/05/24/in-depth-review-of-the-acer-aspire-easystore-h340-windows-home-server/) as a central library for my music files and stream wirelessly to my 24 inch white C2D iMac.
It works really well and shows up in Finder automatically (you just have to log in with password to access files).
I can drag and drop files from Mac desktop to WHS box easily and there is an WHS option called folder duplication which mimics RAID-1 if enabled and you have two hard drives installed and keeps copies of specified folders on both hard drives.
The psu fan in my Acer Easystore H340 (I think 60 mm) is too loud for my tastes if in listening room itself, but shouldn't be a problem since you have to connect it to router anyways.
Responsiveness while streaming music is excellent, but I have found that for using the WHS control panel and large file transfers, transferring from a hard wired computer is best (I use a Windows 7 box hard wired with ethernet cable to rip music files to WHS box).
Acer Easystore H340 does get down to about $300 or possibly less occaisionally on sale. Cheaper option is HP MediaSmart LX195 off of eBay with added external storage to enable folder duplication option.
There is also a My Movies for WHS add-in that allows you to rip media disks directly into the WHS box if you add external optical drive to system Connecting keyboard, mouse, and monitor directly to WHS box is easiest, but you can Remote Desktop from another Windows box too.
http://www.pcmag.com/article2/0,2817,2189704,00.asp
