I'd say something like a GT 730 DDR5 is about the best you could choose. One, it's not very demanding in power. Two, it's compatible with older motherboards. Three, your CPU is old enough to not be able to handle certain types of modern games, so there's little reason to pay for something more powerful than a 730. If you're not gaming then something like a GT 710 would also be acceptable. And yes, I suggest a 1gb or 2gb vram card. You won't benefit from a 4gb card, and I wouldn't buy a 512mb card either.