What 500W power supply are you using? If its a generic model, I wouldn't feel safe with you using that very nice GTX570 on it.
You could get a new power supply and a good card for a good price now still.http://www.newegg.com/Product/Product.aspx?Item=N82E16817139028http://www.newegg.com/Product/Product.aspx?Item=N82E16814150617
That should come out to like $290 without shipping, and you should be able to play most of those games on high resolutions. If you want to go a little bit cheaper, you could go with this power supply instead, that is very highly rated:http://www.newegg.com/Product/Product.aspx?Item=N82E16817151093
EDIT: Forgot to add that this combo is going to perform well in all these games. It probably wont run BF3 on Ultra @60, but it will run it very smoothly probably above 40 or so.