What are you gonna use it for?
Gaming, 7600K
Web browsing, 6600K
Productivity, 1700
Right now more cores only comes in handy in a handful of games, you should look at the benchies for games you play, and use that to decide. In the future, it will be more important to have more stronger cores, but by the time that comes to pass more than likely there will be newer processors to choose from, hopefully AMD can put enough pressure on Intel to make Intel come out with 6/12 or 8/16 processors for the mainstream.