I am looking at upgrading my graphics card, and I want great performance for WoW, but I'm not sure how much more performance a 660 will have over a 560
The 560 should be sufficient for 1920x1080 ultra settings in WoW, even during 25 man raids. You won't be able to run AA and full AF though. The main question is what CPU do you have? This will be a huge factor for performance in WoW. The 660 is a better GPU but likely won't make too much difference for your needs.
I really want to upgrade my gpu, and i have the AMD Athlon ll x3 455. I need to know if this will work. Should I unlock fourth core? or overclock? or just choose a different gpu.
If you want to see a big performance increase... keep your gtx 560 and get a new CPU + mobo + ram... If you want to throw away $200-$240 for very little performance gain buy the gtx 660. Your CPU is holding you back in WoW not your graphics card.
I would not buy a gtx 560... they are way overpriced for the performance they give I thought you already had the 560 and where thinking about upgrading to the 660... I believe the gtx 660 is about 50%-100% faster than the 560... and only costs like 20% more.
I would say get the GTX 660 now, then save up $140 ish and get a FX-6300... Or save up $100 and get the phenom II 965BE, Although in the long run you will be better off with the FX-6300.