Not silly at all since i inquired the same thing before i bought the 2nd card.
You can, as long as they are the same card. Thats the answer i got back.
I kind of don't like the idea of running the 2 different manufactures so I'm going to trade my evga one over to a buddy who is buying an xfx 8800 gt 512.
So then that will be taken out of the equation.