Yeah, I know
I would drop the second set for now until you can get someone in here with more experience on this matter. I've only ever run 2 sticks with my AMD systems and am only giving advise based on what I've seen others tell people.
Though I am positive the ram can handle more voltage and the cpunb voltage limit is the same as the cpu itself (though anything over 1.45v in my experience has done nothing).
You should take two out and see if you can do 4GHz with a 2.8GHz nb, everything should get a bit more snappy