nawabaarij :
geofelt :
Both are approximately the same performance.
What is the primary use for this?
If you have a Z270 based motherboard, the 7600K can be overclocked which will pay dividends in gaming.
If your main use is batch oriented apps that can use all threads, the 6700 is reasonable.
As to new vs. used, I see no problems with used.
The processors rarely fail.
My main use is gaming with a gtx 1070
And some video editing i have h110m board
I think I would opt for the 7600K.
For gaming, faster single thread core speeds will be more helpful than more threads.
I think it is easier to tolerate longer editing batch runs than to have any stutters due to insufficient cpu speeds.
I would not change out the motherboard.
See how you do.
You will have the option later to change to a Z370 based motherboard if that is what you need.
Here is the potential:
As of 6/19/17
What percent of samples can get an overclock
at a vcore around 1.4v.
I5-7600K
4.9 72%
5.0 52%
5.1 27%
5.2 16%
5.3 samples exist, unknown % of occurrence