The biggest benefit from FreeNAS is ZFS instead of traditional RAID. But, you will need a server grade mobo to get a chipset that supports ECC memory. Look at the FreeNAS rig in my sig for an example. I am using the same CPU with 32 GB of ECC RAM.
And, as you can see, it uses all of it. ZFS is very memory intensive. Basic rule of thumb with FreeNAS and ZFS is 8GB min plus one GB for every TB of storage. For ideal performance at least. ZFS basically thinks all HDDs suck and does not rely on there own error checking. It also does a lot of caching in the RAM. This is why you really should use ECC. If a bit flips in RAM it can destroy your data. It's a low chance but high penalty situation . ZFS is better then RAID though. That being said, you don't want a RAID card in the machine. Either use the mobo in normal AHCI mode or use a dumb HBA card. ZFS wants direct communication and control of the drives.
As for the CPU, it works fine for most tasks. But 1080p transcode from MKV files I made from Bluerays takes all the CPU can give. Really needs more power for that. At least with plex. If just sending files around it should be fine.
Here is a lower spec version of my mobo, c222 chipset. Dual GB plus a 3rd port for IPMI. IPMI is kinda nice for a home network. You can load the FreeNAS ISO to a virtual CD-ROM from a console and remote run everything. Even BIOS is accessible remotely over IPMI. Pretty handy. My server has never had a screen or keyboard hooked to it.
My mobo has the C226 chipset. Main reason I went with this is for 6 x 6GB SATA ports.
I would ditch the Dell card and get some ECC and a server board. Then use FreeNAS/ZFS.Edited by Prophet4NO1 - 2/15/16 at 8:09am