I'm using a Xeon-D machine, quad cores, with ECC DDR. It's overkill for just storage, but I also run a bunch of VMs on it. It's my router (pfsense), my storage box (samba w/ZFS on SSD array), my ssh utility knife, my "run vendor crapware" (e.g. Lutron's RadioRa software) Windows box, etc. QEMU is fantastic.

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.