I'm pretty sure you can run supreme commander on both monitors, depending on how you have your monitors set up with windows/whatever os you use.

I'm also pretty sure the performance would go through the floor, at least on the second monitor, it being run off a smallish card.

And that's why you need four 9800 cards, each pair of two in sli, running independently of one another.
We could call it Nested SLI, just like raid volumes, SLI 0+1!