650Ti Boost is a good choice not that far from the 660 in performance
The HD 7850 is also a good option, The following chart will give you an ideahttp://tpucdn.com/reviews/NVIDIA/GeForce_GTX_650_Ti_Boost/images/perfrel_1920.gif
Thank you for the information. Should I be concerned at all with my current system (i.e. CPU, RAM, etc.) bottlenecking the graphics card performance? (I am just curious).
With that CPU occasional bottleneck can not be denied in some modern games, but @720p or 1080p gaming @ high graphics its ok. Adding some more memory will help gaming. Thanks