A much better solution is the Drobo. It retails for $500 and can have a network attachment added to make it a network attached storage solution for a little extra. It is the most advanced form of storage (Data Robotics) and will guarantee to be the safest and easiest storage manager. It protects your data in the event that one of the hard drives fails.
It can hold up to 4 hard drives of SATA connector type. They can mix and max brands, sizes, speeds, etc. You could use a 150GB Raptor, a 500GB Seagate 7200.11, and a Maxtor 200GB 5400rpm all in the same machine.