That case has two fans, one intake and one outtake, thats is fine.
The K means it has an unlocked multiplier making overclocking easy.
The speed is a sum of 100MHz (for the base clock) and the CPU multiplier of say 35x for the 4690K, that is how it gets 3.5Ghz or 3500MHz.
If you change the multi from say 35x to 40x you will have a 4GHz CPU.
Thats a simplified explanation of it, but the CPU also has speedstep and Turboboost.
Cheers, if I decided to keep my case how can I check on whether the CPU cooler will fit?