I'd recommend HD7950. They are $300 while HD7970's are $400. Assuming your resolution is 1920X1080 or lower, the 7950 will be fine. It can be overclocked quite a bit for performance nearing or surpassing the 7970 for the 7950 tends to overclock better.
I'd recommend getting:http://www.newegg.ca/Product/Product.aspx?Item=N82E16814125423
GIGABYTE GV-N670OC-2GD GeForce GTX 670 2GB 256-bit GDDR5 PCI Express 3.0 x16 HDCP Ready SLI Support Video Card