You'll currently have four, two intake and two exhaust right? With what I posted, that should give you four fans exactly the same. Two for intake, two for exhaust and those should be plenty for 90% of configurations, even for high end overclocking. At some point down the road you MIGHT decide you want to go with higher end fans, like the Noctua NF-A14 PWM or NF-A14 PWM chromax.black.swap fans, which likely move more air and are certainly quieter, but see how you like those for now. If you wanted, instead of getting another fan just like the ones that come in the case, you could opt to go with a Noctua fan now, that way if you decide to do that later you only have to buy three of them instead of four after having already bought a Fractal design fan.
They are more expensive, at about 25 bucks a pop, but they are worth it. ALL I will run in my machines are Noctua fans.