I do not much like all in one liquid coolers when a good air cooler can do the job.
A liquid cooler will be expensive, noisy, less reliable, and will not cool any better
in a well ventilated case.
Liquid cooling is really air cooling, it just puts the heat exchange in a different place.
The orientation of the radiator will cause a problem.
If you orient it to take in cool air from the outside, you will cool the cpu better, but the hot air then circulates inside the case heating up the graphics card and motherboard.
If you orient it to exhaust(which I think is better) , then your cpu cooling will be less effective because it uses pre heated case air.
And... I have read too many tales of woe when a liquid cooler leaks.
google "H100 leak"
The stock cooler would allow you the oc you listed.
But, it can get noisy under load.
A simple tower type cooler with a slow turning 120mm fan would cost $30 in the US. cm hyper212 or Xigmatek would be 2.
For the very best look for noctua or phanteks with 140mm fans.