I think quite a few on
TE are currently in the same predicament, including yours truly.
Someone suggested an atom based PC with Windows Home Server. If the mother board can support RAID (I dont like software based RAID) then it probably is a very good setup.
1. Atom based CPU+MB+RAM = 20W ...add approx. 2.5W per drive for a WD Green and 4W for a Seagate Barracuda = 30-35W
2. RAID5 setup = Loss of 1 HDD space but will ensure 0 loss of data even if any of the drives fail (only 1 at a time though)
3. Can work headless so just shove it in a corner after setting it up.
Its definitely better than 50-200W PC and more if its a gaming rig. Only issue is I am not sure if they have RAID5 support onboard.