I am using this board http://www.amazon.com/gp/product/B00JQHUE3G?psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00
This model has four SATA ports. I am using four Hitachi 2TB drives along with 4GB of ram. Works great. I would like to find a small case to put it all in but most ITX cases seem to limit you there, except for a Fractal Designs NODE 304.
My old Hitachi drives are not super efficient and still my setup uses only 40W at idle.
I also have the cheaper two SATA version with the ATX form factor I am using as a PFSense firewall. I used the ATX version since I had an Intel quad port NIC that I wanted to use. http://www.amazon.com/dp/B00JO1DIIM/ref=psdc_1048424_t1_B00JQHUE3G
These are really slick little setups. The processor runs at 30 degrees C or so, they only pull 10-15W, and are dead silent with no fan.
I was using a G3258. This processor is almost as powerful while pulling way less http://cpuboss.com/cpus/Intel-Pentium-G3258-vs-Intel-Celeron-J1800
Here is a site you can compare specs with. The power to performance is hard to beat http://cpuboss.com/cpu/Intel-Celeron-J1800