Video Card Question

I have MS Flight Simulator X installed on my system. However it seems to run slow. The frame refresh rate is like 2x per second and it runs even slower if I enable a lot of enhancements. I have a 2.8 GHZ processor and 1.2GB RAM, but only 64MB video memory. Would I see an increase in performance if I upgraded my video card to let’s say 512MB? I think 512MB is about the limit as my mobo only supports 8x agp.
Thanx
Jim
Sorry about the double post I was not getting any replies on the Gaming forum.