don't go with the 660, buy a 7870 which is currently 234$ on newegg..
it will be a grat choice :http://www.newegg.com/Product/Product.aspx?Item=N82E16814150605
The GeForce GTX 660 comes with clock speeds of 980 MHz on the GPU, and 1502 MHz on the 2048 MB of GDDR5 RAM. It features 960 SPUs as well as 80 Texture Address Units and 24 ROPs.
Compare all of that to the Radeon HD 7870, which comes with core clock speeds of 1000 MHz on the GPU, and 1200 MHz on the 2048 MB of GDDR5 memory. It features 1280 SPUs along with 80 TAUs and 32 Rasterization Operator Units.
no need to buy a gtx 660 for $299 when you can get better performance with a 7870 which is currently $234.
Go with the 7870