U can get get HIS 7770 for $125. This is 20-25% faster than 7750 but u need a good 400w psu with pcie connector.
Thanks "raheel167" for your reply. Can you please explain me little more about the "pcie connector" as you mentioned earlier. Is there any additional card required to support the HIS 7770 or will it work with my i7-920 DX580SO configuration?
ASHISH65 - Can you please explain little more about how to verify the +12V power supply rating and what is the significance of it? Please excuse for asking very basic questions, but that will help me in improving my knowledge base.
raheel167 - The maker is Cooler Master.
Using Google I found the below link from newegg to calculate the wattage requirement and it returned 384W PSU requirement for my system configuration.
Gtx 650 is little better than hd 7750.but gtx 650 needs 6 pin connector and you need to upgrade your psu.but hd 7750 is best choice even it hd 7750 at its peak load consumes just 43w.just go with hd 7750.