Hardware for NAS

Hello All,
I am having trouble figuring out what hardware i should use for my new NAS build.

I was looking at server hardware and desktop hardware. I am unsure if i should try desktop hardware as it lacks ECC but server hardware is so much more expensive. The system will be left on 24/7, so reliability is a huge concern. I plan to use two NIC's to speed up the connection to the network. It will also be a headless system, but would like the ability to connect a monitor for configurations. I was planning on running a baremetal NAS setup.

My main concerns in near equivlent weight are:
-reliability
-Power consumption
-cost
-speed


For CPU's I thought of:
-i3 2100
-xeon e3 1220 v2

Those both belong to the 1155 socket type as they are a recent technology, any alternatives would be welcomed.

The other equipment various depending and the processor.

Also, i am debating between using 3.5" drives or 2.5" drives. I have heard mixed opinions on both. I would welcome anyone whom has some experience with both to offer their knowledge.

Next year i plan to expand the system by adding a EXSi server to manage all the computers throughout the house via thin clients, any alternatives or experience in this regard is also welcomed. I planned to build it all at once but i am still lacking the knowledge to make the ESXi server with any kind of intelligent plan, but i am in dire need of storage. I was thinking of building a small server cabinet to house everything later down the line as well.

Thank you much,
Terry