what resolution and what games? what are your other system specs? If a higher resolution, keep in mind you may need more than the options given, where the 660 would probably be weaker due to lack of memory bandwidth. For higher resolutions, the 670 or 7950 would be a better solution.
If you are at a moderate resolution, such as 1920x1080 or 1920x1200, the mentioned should be fine, depending on the games and settings.
3770k WC + Sapphire 7950
16GB RAM on MSI Z77A-GD65
HP ZR30W | Haf X | Crucial M4 | Logitech user