On the Intel side, the Core i5-2500K in the overclocking value in the Sandy Bridge lineup.
Did you consider the Samsung HD103SJ Spinpoint F3 for your hard-drive? It's almost as fast as the Caviar Black while being cheaper, quieter and cooler. You don't want to use the slower Caviar Green for your operating system.
The Radeon HD6870 is noticeably faster than the HD6850. For the small difference in price, that's the card to get.
Given a choice, I prefer to use 120mm cooling fans rather than 92mm fans. You can get more cooling with less noise from the larger fan.
i7-6700K, NT06-Pro, GA-Z170N-Gaming5, 32 GiB, 980Ti, SM951, 5TB HDD, Blu-ray, FTZ01, SX600-G, 3007WFP+2001FP, RK-9000BR, MX518