I have roughly the same requirements. For me it worked out more time and cost efficient to just leave the PC on. Logistics, management and maintenance were a pain when I had a NAS.
My home's IT power draw is about 45 watts, using two access points, that server, and a bunch of little widgets (e.g., Rainforest power monitor, Lutron bridges, etc).
That will go up when I add a big switch, but it's not bad for the utility I get.