Building a new pc in the 1500-2000$ range and buying a 780gtx evga acx for it
Trying to get the most bang for my buck, what are some good cpu's that will last a couple years before being obselete in gaming (replacing 2600k). Video card is running me 700$ after warranty so 800-1500$ left for the rest (case/mouse/keyboard/monitor not needed)
2600k is still up there at the top. unless you absolutely need a hex (or more) for professional purposes then it's not a worthwhile "upgrade" even then it's doubtful you'll notice any difference in games, perhaps in the large multi-player maps of a few games.
Well if you've got to go the more cores route there's sandy bridge-E & the hex 3930k, or just on the horizon are the ivy bridge-E cpu's - however that will be at least a couple months away. ivy / haswell lga 1155 / 1150 i7's will be fairly parallel to what you have now, however the motherboard feature sets could offer improvements to multi-card configurations, storage, expansion, audio, ect. either way i'd be going for a upper mid range z series mobo & a k series cpu.
In that case i'd be thinking primarily about what feature set you want from the motherboard & which mobo offers the best measure of "future-proofing" i'd then select an appropriate K-series cpu to match.