FreeNAS CPU + Mobo Recommendations?!

[BaconFenix]

Hi,
the past few weeks I've been looking at storageg solutions and I have come to a conclusion a own-build FreeNAS system.
And now I have some problems determinating the best mainboard+CPU solution because I have no idea what really impacts the performance of the NAS.  (In comparison to a gaming pc where alot of benchmarks exist for various games to find the right choice...)
I would like to have your advice on this.. my budget for CPU and Motherboard is around 350USD and I'm looking for a combination in a mITX format that brings the best power efficiency*/performance
I already had a look at the ASRock C2750D4I but for 410USD a little expensiv for my taste.

 

Usage: It will run ZFS, multiple filecopies and streaming via Plex should be no problem

Other information:
Case: Fractal Design Node304
Ram: 8gb single non-ECC (ECC RAM support would be nice, but has no priority) (I will pick it up after I've decided for a mainboard)
HDD: 4x4TB WD Red will be in the final build (at the beginning it will run with only 2)
NIC: Dual 1Gbit port intel PCI-E 4x
PSU: BeQuiet Pure Power L8 300W (a buddy sold it for 10bugs and I couldnt say "no"...)

power efficiency*=it will run almost 24/7 so atleast the idle power consumption should be good so my power bill won't explode

I would love to read your recommentaions.

Sincerely yours Baconfenix (aka Max)

 

[BaconFenix]

Thread can be closed, I went for a i3-4160T and Gigabyte H97N-wifi.