i mean your opteron will not be able to run both of those cards without bottlenecking them.
it will run one pretty darn good, but even then it is the weak point in the equation. no offense, my 3600 is my weak point...its just the way it is.
to put it into perspective, look at it like this...
in 3dmark (yes i know its a bunk example) you get a certain score. as you overclock your cpu, your score goes up. but, you reach the point where your cpu will not clock any higher. but, if it could, your score would continue to go up (ie the card would begin to use the resouces availible to it). ya feel me? this is one reason why you may not see a big difference in your score if you overclock your CARD. but, if you overclock your cpu, the difference is massive.