I would suggest to avoid wd reds. Although I have not used it myself or have any personal experience, I have heard lot of complaints from dealers here in mumbai about a bad batch and lot of rma.
Rma also is taking too long for wd. So just think about this.
I just got an upgrade for my freenas server yesterday. I opted for WD AV-gp drives (3tb 30EURS) after hearing so many complaints about the wd red and also the price hike of the hdds.
http://www.techenclave.com/communit...y-show-off-thread.57621/page-370#post-1839048
My suggestions for the freenas.
Please dont spend money on ssd as freenas is loaded from the usb stick. I am using old freenas, but it doesnt make any difference as the freenas os will always be on once booted.
Dont spend insane money on ram. 2gb-4gb is more than enough. I am using 2gb and with 30-40 users my ram usage has never crossed 20-25%
choose the mobo/psu/hdds properly depending on budget / requirement as you dont want these to fail.