+1 ^ The i7-3770 @ stock will perform better than the 2700/2600.
So, if you do not plan to overclock now or even in the future, get the i7-3770. non K version.
If you plan to OC, say 4-4.5ghz, get the i7-3770k.
And if you are planning to achieve a high OC, like 4.5Ghz+, then I would suggest the i7 2600k.
An overclocked 2600k would be just as good as the 2700k, the only difference would be that the 2600k was cheaper.