You will most likely need to run two sets of drivers, one for the 785g integrated and another for the 4850s. So far only Windows 7 can support multiple drivers running at the same time.
My question to you is why do you need to use the 785g integrated card? The two 4850s can support up to a total of four monitors by themselves.
just out of curiosity in regards to a project that I'm planning.
thought the w7 isn't part of it, thanks for the info.