Just in case anyone was curious, I tried out OpenFiler, Ubuntu server and FreeNAS.
I definitely like FreeNAS the best so far. It was easily the quickest to set up and configure. OpenFiler turned out to be just as CLI intensive as Ubuntu server. The web interface for FreeNAS is capable of setting up everything, as well as is small enough to run on a thumb drive I had collecting dust, which leaves all the SATA ports on the motherboard open for drives. You probably can get the other two on a decent sized thumb drive as well, but FreeNAS supports it right in the installer.

Are you running it on a full-sized, real, computer, or on a mini setup or what?

I haven't built an Atom based setup, which is my ideal. I am running it on my old desktop which is a Core2 6420. I am not using it practically at this point either because the hard drives in it are hooked directly to the motherboard and using software RAID as I haven't had time to migrate the cards from my main system to it. I will probably work on that this weekend.

I am waiting to build the Atom system and probably buy new drives once I am confident in the stability of this test rig.