Running multiple GPUs

[Zenaku]

I am trying to run 3 22' acer monitors together. Currently I am running duel monitors using a XFX 2gb HD6950 which cost me $300. I rly dont wanna pay that much again to run a 3rd smoothly. I have found a XFX 1gb hd 6770. My question is, Can I run the 6770 with my 6950 together to support 3 monitors? Or do they have to be the same GPU??

Question do you have AO/DOF on if you do then try turning it off and see if you can run the 3rd better.