560Ti best bang for buck nvidia card out there
460 is pretty much the only worthy 400 series card and its slower but a large margin comapred to a 560Ti
470 and 480 are end of life aka no longer being made and have high heat and extreme power requirements.
depending on your location in the world i can try finding a good price
but for say $270 560ti or AMD 6950 1gb are your best bets.
Fastest 560 Ti available.
Gigabyte Super Overclock $259
Core clock 950mhz
http://www.newegg.com/Product/Produc...-369-_-Product
2nd Fastest 560Ti available.
Asus Direct CU II OC $249
Core clock 900mhz
http://www.newegg.com/Product/Produc...-425-_-Product
3rd fastest 560Ti available.
MSI Twin frozer II $245
Core clock 880mhz
http://www.newegg.com/Product/Produc...-565-_-Product
all 3 cards have better cooling then stock cards so they run quieter cooler and will give you slightly better overall performance compared to stock 560Ti's
Review of the Gigabyte GPU here
http://www.guru3d.com/article/gigaby...-soc-review/11
Note that the GTS 450 = 8800gtx in performance roughly also take note of where the stock 560s performance is compared to the Gigabyte card. sometimes its worth paying a bit extra so you dont have to mess around with overclocking yourself if your not familar with it.