Listen to the Cat, he may be moose obsessed but he talks sense otherwise
You seem to like Nvidia cards, we can advise but need to know budget. For example, a GT460 will be massively faster than a 220. Double the money gets you from 48 shaders to 336. Thats a factor of 7. Those shaders are clocked higher as well, and you get a faster memory system to keep those shaders fed with graphics data. That may not be the best card for you, but I can be fairly sure a GT220 is the wrong one.
The only reason I sway for Nvidia is simply every PC I had used the Nvidia card, however if ATi have a better card within my budget I'd buy the ATi without a doubt.
The thing is, better graphics cards can be hard on the PSU, hence we need to know exactly what PSU you are running as that may need to be updated too.
Your CPU should be fine. Unless you are looking for an excuse to change it, and we have all been there I'm sure