Try it, I know I tried my main vid card that was part of the mother board then my radeon, it didn't allow it. It was pick one or the other. Worth a shot... They do have special switchers out there for more then one monitor... Can try that... Also there use to be something called SLI mode, you attached the same video card to each other and it had dual power etc... Was sick ****, not many cards do that... I don't know of any really, however 3dfx (RIP) had that perfect with the Voodoo2.
"The ghost... Was never there and you'll never see me"