When I answer this topic I didn't saw your post yet................
Anyway about PC games I have no idea
Becuase my VGA have no FSAA but PSX games many people have post screenshot here so I can tell you
i think 800 x 600 wil be surely better with that cpu.
i think you really need to replace your cpu .
you must have a cpu thats capable of supplying your geforce with
the needed number of polygons /s to have a good fps (frame per second) .
so if you mentioned any slownes at the emulators be sure that the cpu caused it.