I recently got a 660 for slightly over $200. It blows away the 650, and beats the 7850 in nearly all cases, often beating the 7870.
In many cases, it also beats the GTX 580. So you would be at the previous-gen's flagship mark.
But if you're keen on AMD, the 7850 all the way. Or for a few more bucks, shell out for a 7870 and beat all the cards you mentioned. But like Django above said, just make sure it has plenty of RAM, like 2GB. As soon as I upgraded, I was quickly using about 1.5GB+ in games. So 1GB won't cut it. Not for an upgrade, anyway.