I have a i5 2500k @ 5gigs and that's still fast enough to run most games with my GPU which is an EVGA GTX670 FTW. Then I have 16 gigs of RAM but you would probably just about get away with 12. Motherboard wise do not buy Asus and make sure its water cooled I have a Khuler H920 and its awesome.
Gaming keyboards are shite get a Filko 10 keyless or DAS and a decent 7.1 USB headset for sound.
For the case don't touch anything other than Coolermaster
Mice never ever get anything that's not from Razer.