The i5-6600k is very powerful, it will power any single GPU without a hold-back, GTX 980 Ti will work really well with it.
I was thinking of upgrading from a 60hz 1080p monitor to a 1440p monitor . How would the CPU and GPU run on this ? Also could you recommend any 1440p monitors , specifically for gaming?
The i5-6600K with a decent overclock is arguably the strongest gaming processor you can buy today, bar none.
If you will play fast action games on a 4k monitor, only then might a single GTX980ti be the limiting factor.
FWIW:
As of 2/16/16
What percent can get an overclock at a somewhat sane 1.40v Vcore.
I5-6600K
4.9 11%
4.8 38%
4.7 70%
4.6 83%
14nm runs cool, no exotic cooling is necessary.