I own an r9 290 and an i5 6600k overclocked to 4.5ghz on stock volts. As newer i5's and i7's will easily max every game without an overclock.
However on gaming the difference between the 6600k and the 6700k should be very minimal in difference.
Now Im not sure what games you will play, but.
Just Cause 2 benchmark= 115fps average.
BF4 with mantle and 2xmssaa ULTRA= 85fps average and minimum of about 67 of what I saw.
In Uniengine heaven benchmark I got a score of 1704 pts and avg fps of 67.6fps.
Shadow of Mordor= avg 77fps. min 44fps. On the benchmark.
In 3Dmark I ahve seem to have lost my results...
THIS IS ALL ON 1920X1080. So obviously at 1080p the r9 290 will max almost every game easily. The CPU (especially high end CPU's) are less important in gaming and your performance in games leans heavily on GPU performance.
On higher resolutions you will see some settings you will need to turn down.
Here is a video with some more benchmarks.
https://www.youtube.com/watch?v=vhPD4Qdm1lE
-good luck