I haven't read the whole thread, but I just wanted to second the freeNAS suggestions. I can't imagine a more economical way to come out with a VERY powerful storage device. Mine cost me ~$350 for the case, processor motherboard, RAM, power supply, SATA controller, and NIC. Even at that cost I was still able to get a haswell based dual core processor in there. I may have gone a bit light on the processor though (pentium G3220), as it seems to only be able to handle one 1080P or two 720P streams simultaneously. That's still way better than NASes that cost over double what I have in mine, and hey I can always drop a better processor in there whenever I want. In fact I could easily make my NAS more powerful than practically any consumer NAS out there without spending much at all. Never going back to premade.
"Learning" freenas isn't really something to worry about either. It's well documented and the only real snag I hit with it was the fact that my motherboard's NIC wasn't supported despite being in the list of supported hardware. An add-on NIC fixed that up. The web GUI essentially works just like any other NAS interface though.