pick up a 5570 nvidia is terrible low/mid for graphics. I have a 9500 gt xfx and it is pretty mediocre unless you are playing anything less than sc2. Playing at 1280/1024.
Barley get constant 30fps for bfbc2 on low on a q8300/4gigs ram
the 9500gt is the better of the two by a slight margin i believe. Both cards not worth the effort, not much of an upgrade over even onboard gfx. as said above a 5570 would be better, but still slower than what you would want to play any recent game on more than low detail settings. A minimum gaming card would be an ati 5750 or nvidia gts450 IMO. But if your not using it for games, get whichever is cheapest.