No, I doubt the graphics will be any better...running more than one thing at a time relys on your cpu much more than your gpu...
There is not a real noticable difference between DVI and VGA...especially on screen sizes 19" and less.
Yes, I don't doubt you can setup a quad display, but if you are not going to be using the quad setup much, it would be better to use one graphics card. 2 graphics cards won't help in one game unless you have an SLI, or crossfire setup.