After being not very satisfied with OpenWRT on a router as a fileserver (it's great overall, but file transfers are just too slow), I'm now using an IFC6410 as my home server.
It doesn't use much more power than the linked NAS device, but comes with basically the same hardware as the Nexus 4, on a nice board with all those useful connectors. Quad-core 1.5 Ghz CPU, 2GB of RAM, SATA and Gigabit ethernet.