Yeah you will want to do that in the bios.  On my Asus B250 its pretty easy to find but you might have to search around some depending on what motherboard you have.  But you are on the right track.  It is nice because you do not need a power switch.  I have my gpu's powered by server power supplies and the motherboard on a regular atx and to power off I just turn off the atx power supply.  When you turn it back on the rig should instantly boot back up just like with a power outage.