You could probably build a setup just like that for less than $2200. The Hitachi 3TB drives are about $190/each ($760) leaving you with $1440 to build a small little PC to manage them and likely keep a 5th 3TB HD running as a hot spare.
Although you could just buy one of these sans-digital (seems to be a terrible translation to me) external enclosure for ~ $150 . Probably cheaper than trying to build something from scratch.