You should look into an UnRaid Server, http://www.lime-technology.com/. I've been using one for about 4yrs now. It's very simple to operate and works flawlessly. You can start out with two drives, one is parity and one data. When you run out of room, simply pop in another drive of any size and type as long as it's smaller than the parity drive. I currently have 10TB of drive space with my server capable of going up to 30TB. If any one drive fails, pop in a new one and the data is rebuilt.

I store all my full copy blu rays and dvd's as well as music ripped to wma lossless and flac. I then run an HTPC with Windows 7 and MCE.