the i7 970 is a hexcore with hyper-threading (i believe), and is the highest core count with hyperthreading they have.
Personally, the i5 2500k for gaming is your best bang for buck, and your i7 2600k is for multi use processing with applications and gaming. I see no need to go with anymore unless you are doing professional work, and then you should probably refer to a professional in the same field as you, and see what they use from personal experience. i5 for gaming is more than sufficient with a high end gpu, and an i7 for SLI.
I know i hit on other things than what your OP was, but back to that, the i7 970 is i believe a 6-core with H.T.