can you maybe suggest a nvidia card?
Since you only have a small upgrading budget to work with... an AMD GPU will be your best bet.
AMD = better price to performance.
NVIDIA = better overall performance but cost more.
here are the 7970s: http://www.pccasegear.com/index.php?main_page=index&cPath=193_1309&vk_sort=4
ignore the ASUS ROG ARES 2 for now. (that is 2x 7970's in Crossfire on 1 Single Card)
and here are the 680's: http://www.pccasegear.com/index.php?main_page=index&cPath=193_1377&vk_sort=4
As you can see the price is huge, here is the benchmark details: http://www.anandtech.com/bench/Product/508?vs=555
^^ keep in mind I used the standard 7970 and standard 680, the 7970 performs better than the 680 in some scenarios and the 680 performs better than the 7970 in some scenarios, and as I have linked above the 7970 of a budget like yours is a lot cheaper.
Now let's get too the 7950 vs 670: (which is what you will want to know, the 7950 is usually paired with the 670 or 660ti, I used the 670 in this scenario).
As you can see the price difference is quite large: (hence your budget)
here is the benchmarks between the 2 cards: http://www.anandtech.com/bench/Product/550?vs=598
As you can see the 670 and 7950 are very close in benchmarks. 670 wins in some and the 7950 wins in some.Therefore my recommendation would be a 7950.
If you had... $800-1000 to spend on a new CPU and GPU upgrade, you'll want to go for a 680 and a 3570k or a 3770k, there is only be a 1-3 fps difference between the 3570k and the 3770k in games. If you seriously considering going with NVIDIA then save up some more $$
NVIDIA = better overall performance but cost more.Edited by BrighteousPony - 3/27/13 at 1:21am