What i5 and i7 CPU is "unlocked" ? Difference 2600k /2600s /2600?

[Mfusick]

What is the difference in the LGA1155 CPU's?

Which one would I want to match on an ASUS LGA1155 Mobo if I wanted to overclock it ? (aircooled)

 

[bryanW1995]

K series is unlocked, that's the one you want. 2600 is the standard cpu. 2600s is low power 65w but lower clocks, with very aggressive turbo that allows it to perform nearly the same as the same as 2600 on up to 3 of the 4 cores. If all 4 cores are enabled then turbo will only get 2600s up to 2.9, however.