When Should I Purchase A 8700K?

Solution
When you are ready and with a budget, you should ask someone here to select PC parts for your build. Just want to point out with your choice H100i for CPU cooling in Corsair 750D case, you don't need to buy 8 additional 120mm fans since you don't have any space to install them.

When you are ready and with a budget, you should ask someone here to select PC parts for your build. Just want to point out with your choice H100i for CPU cooling in Corsair 750D case, you don't need to buy 8 additional 120mm fans since you don't have any space to install them.

 
Solution
@Bob125484 Thank you! And the reason I chose to buy 8 extra fans is because not only am I going to replace all the stock fans in my case, but also my stock cpu cooler fans.