Go for a AMD 7850, its a little bit better than a 650 ti. Mine plays most games on very high settings just fine. The lowest in settings i have had to go so far is High, one down from ultra. That was with some at ultra still too.
If you can catch it with a MIR you maybe can get it right at around $150. I got mine in May for a final cost of $144.
If you do not want to wait for a good sell, go for the AMD 7790, its worse than the 7850 but only a little. It can still play plenty of things on high. I've seen them as low as $120