I am currently working on the parts list for my first build. I do like my fair share of games but I wouldn't consider myself a die-hard PC Gamer. The Games I Would Like To Play:
Not really an OC fan, as I don't want to screw something up.
I will be running one 1080p monitor and will be probably running a PSU anywhere from 650-750 watts.
I really don't mind AMD vs NVIDIA. I'm just looking for the best bang for my buck.
These games that you are going to play mainly favor nVidia so I guess GTX 660ti is your best choice BUT thats if you meant cards under 300 Dollars. If you meant 300 Pound Sterling, I guess GTX 670 will be your best choice.
I was thinking about the 7870 or 7950 and I'm talking about USD, sorry for the confusion.
HD 7950 is a very good card, but I recommended the nVidia ones because their benchmark results in the games you listed are higher than the AMD ones especially BF3 and Starcraft II but on one monitor, the difference is not going to be felt so go with the 7950 or the 660ti, you can't go wrong with either. Considering the HD 7870, the 7950 is better than it with at least 10-15 fps more in games you listed I guess.