I currently building my first build i play games every day and i want a good gpu and res will be 1680 by1050 heres my chocies are hd 7770 for 134 dollars,hd7850 $ 250 hd 6870 $130,hd6850$145,gtx560ti$240 if anyone can help me my specs are phemon x4 840 4gbs i havent got psu yet
In my opinion you have a 4-core CPU, as games in the future will use multi-core CPU's, your CPU will become more useful over time. As long as you have sufficient cooling and good airflow in your case, an overclock will help. You don't have to necessarily have to OC your CPU unless you want serious performance from games like Battlefield 3, the upcoming Crysis 3, or a benchmark game like Metro 2033.
The 7850 is a great card, I think it goes well with your CPU.