Your best bet is HD 6670 GDDR5 version:http://www.newegg.com/Product/Product.aspx?Item=N82E16814127586
That's the fastest card below $90 AND it will work with your power supply. It will play both BF3 and Crysis 2 nicely. Not maximum settings, but you should expect medium-high at your resolution.
Wow, I was considering it, but I thought it worked on a very high PSU... Thanks A LOT, I didn't expect such a quick answer! Oh and BTW, what is the difference between GDDR5 and DDR3? I would have a cheaper deal for DDR3 :P