Also would a GTX660 or HD7870 bottleneck my cpu even if it was overclocked to say 4.0ghz
http://www.scan.co.uk/products/2gb-msi-gtx-660-twin-frozr-iii-oc-28nm-pcie-30-(x16)-6008mhz-gddr5-gpu-1033mhz-boost-1098mhz-cores-9
http://www.scan.co.uk/products/2gb-msi-radeon-hd-7870-overclocked-28nm-4800mhz-gddr5-gpu-1050mhz-1280-cores-dl-dvi-i-hdmi-mdp
Also from looking at results the 7870 only seems to have a 1-3 fps difference compared to the gtx 660
http://www.scan.co.uk/products/2gb-msi-gtx-660-twin-frozr-iii-oc-28nm-pcie-30-(x16)-6008mhz-gddr5-gpu-1033mhz-boost-1098mhz-cores-9
http://www.scan.co.uk/products/2gb-msi-radeon-hd-7870-overclocked-28nm-4800mhz-gddr5-gpu-1050mhz-1280-cores-dl-dvi-i-hdmi-mdp
Also from looking at results the 7870 only seems to have a 1-3 fps difference compared to the gtx 660