My board is the GA-MA78LM-S2H from Gigabyte and it definitely can unlock the 4th core in a 720 because that's what I did. The GA-MA78LM-S2 will also do it (the difference between the two is the S2H has HDMI output with the onboard video card).
However, it is a crap shoot as to whether you get a 4th core to unlock and be stable. I got lucky. I didn't have to adjust any voltages or anything. I hammered it with Prime95 for about an hour and decided that was enough. I know some say you need to do it for 24 hours, but that's seems excessive. If the thing doesn't hiccup within an hours, I say that's plenty for me to determine it's stable.