Are you buying the OS? Buying a new monitor? Overclocking? What other kinds of games are you playing? Black Ops II isn't a very demanding game, but we don't know what you mean by 'other games like that'.
* You could upgrade the GPU to 7850, but it'll be around $170ish (about $80 more). The AMD 7790 is coming out soon, which would be better than the 7770, but less than the 7850. It would be around the $140-150ish range in price (not sure on final pricing yet).
Thanks for all the replies guys. My budget with an OS would be around $500. I won't be overclocking anytime soon. I would like to play Far Cry 3, AC3 , and other COD games.
You just named an EXTREMELY demanding game, a game that requires a decent CPU, and the COD games, which could be maxxed out by a limp fish's erection.
Also, you aren't going to get what you're looking for for $500, including the OS - you'd get something that can play COD just fine, can play AC3 on (probably) medium settings, and would croak if you even tried to LOAD far cry 3.
That being said, do you already have a monitor? What resolution is it?