I looked up the Nvidia card you mention above. It isn't just PCI, it is PCI-Express, 8-channels. It's output is through a BNC connector, in a SERIAL signal of some kind. And it's $2,690. A tad pricey.
And the first board above probably uses the other DB connector to capture VGA video signals. I can't say for sure, but I found boards that do that.
Basically, I think you're up the creek. You might want to consider a two board solution: one PCI 4-channel video capture board, and one suitable video-out board with VGA, RGB, whatever.
Does your PC have PCI-E by any chance? Just about all modern video boards seem to be PCI-E(xpress).
kenjj