If his voltages are odd what would you say about mine?...
(A6-3670K @ 3.1GHz, ASUS EAH5770 CUcore, 2x4GB G.Skill RipjawsZ 2400MHz (but at 1866MHz due to mobo limitations)
You're scaring me.
Hmmmm, is that 1 stick of 4GB or 2 sticks of 2GB? If it's single channel then it's highly likely that's what causing a poor performance. You should get dual channel for AMD CPU's. But even if it's 4GB total in dual-channel, that's still a tad small amount of RAM.
As a comparison, I have 2x4GB of RAM. While playing BF4 at 1366x768 HIGH the RAM usage reaches 60-70%. Not sure about ARMA 3, but I assume it should use about the same or even more, depending on your settings...