Just an FYI with the SuperMicro board... This was my first time using a SM Board, I went with this board because of the 8 port onboard LSI controller. It has been great, except I ran into one small issue with this as well.

These boards don't seem to do well with regular case fans like Noctua's. I got 3 PWM noctua 140mm fans, and it kept revving up to max speed and slowing down every ~5 seconds. Looking thru the logs I noticed that I was constantly hitting the low fan threshold and the fans would rev up to max speed, then realize that my CPU was at 30 degrees Celcius, then slow back down. This was a never ending cycle, and got very very annoying since the box sits all of 5ft away from me.

I read thru this article and things have been much better. I simply lowered the threshold of the fans and all seems to be going well so far! You may be fine with your board, but again this was something I ran into and wanted to give you a heads up.

Lastly, that Xeon processor may very well be overkill. I ended up going with an i3 4370 which according to ARK supports my ECC RAM. However, again YMMV as each person has something different in mind with their builds (plugins, dedup, etc.)!