bob, I'm using a 256 MG card Nvidia GeForce 7800 GTX and it rocks on a 3.0 Ghx Pentium D processor with 2 GB of ram. The screen is completely filled.
With the amount of ram you have the video card should be fine. It might even be better than the one I got - I just don't keep up with them enough to know when mine is outdated
I run CAD software on my computer mainly so I sprung for a higher end graphics card then I would have normally got.