Best Practices for Multiple Video Cards

Hey Folks:

I have a client that wants to drive 6 monitors, 2 each from 3 video cards, from the same PC. Does anybody have any best-practice suggestions for this? Our game engine will support both OpenGL or DirectX, so api is not an issue. We’ll go with whatever gives us the best performance.

Initial thought is to go ahead and create multiple devices in DirectX9 (currently our most used driver.) However, it looks like DX11 has better support for multiple adapters and multiple outputs on those adapters.

Any recommendations on choosing a path would be most appreciated!