yea u can tell 40 from 100 u can feel the difference beetween 70 and 35 on CS:S and my 6600GT gets me 70 frames persecond aa and af all the way up so yea a gt will get u some goodies and different games have different average frames per socnd
It actually gets closer to 70fps before you can't tell the difference.
Just as an experiment, check the hz on your monitor, set it around 60-70, Then, look to your left or right and look at the monitor using your peripheral vision. you should see some flashing. That's because the rods located at the edge of your eye are better able to detect motion than the focused cones in the center. . cool junk, that.
Just an interesting fact, not really pertaining to the business in this thread. For that, I say, if you're getting 50+ fps at all times you're more than good. And that setup should do that.