You could save a little money and just buy an out of the box NAS unit that has RAID 5 all set up already.
I bought one for the office a few years ago and I use it for simple file storage, not backing any important stuff up on it.
How much space are you talking about?
I bought one like this for about $1500 maybe 3 years ago. It's under $400 now for 1.5TB.
Conversely, I also recently bought a cool NAS unit that is rack mountable and has redundant power and gigabit NICS.
It was about $2200 when I loaded it with eight 1TB drives.
I bought a Thecus N8800 for about $1200 and added 8 western digital black drives ($99 each).
http://www.newegg.com/Product/Produc...-028-_-Product