My preferred approach would be to buy four (or more) large SATA disks
and use them as a software RAID5 array.

I've always been fascinated by RAID arrays - especially their ability to
increase the size of your "disc" without ever going offline. However,
for domestic applications, the noise of four or more discs could get
quite distracting.
I used to run a mainframe disk subsystem that contained 60 PC disks. You
couldn't make yourself heard standing near it.

--
Steve Swift
http://www.swiftys.org.uk/swifty.html
http://www.ringers.org.uk