In it's base it's a 680 but with slightly higher clock (theres a msi card with even higher clock) could also go for a HD 7970 GHz edition.
I really like my cheap integrated water cooling (Antec H2o 620) for the price, keeps things way cool even on overlclock (maybe not as good as the "best" air coolers but those will cost more. But if you don't plan on clocking the i5 up for now you can just use the stock cooler and save some cash.GTX 780 GTX 770 GTX 680 GTX 670
Gpu GK110 GK104 GK104 GK104
production 28nm 28nm 28nm 28nm
Cuda-cores 2304 1536 1536 1344
Base-clock 863MHz 1046MHz 1006MHz 915MHz
Boost-clock 900MHz 1085MHz 1058MHz 980MHz
Memory size 3GB gddr5 2GB gddr5 2GB gddr5 2GB gddr5
Gddr5-clock 6000MHz 7010MHz 6000MHz 6000MHz
Memory bus 384bit 256bit 256bit 256bit
Tdp 250W 230W 195W 170W
a SSD i would again really recommend.