The i5-4690K has a stock speed of 3.5Ghz. What is the best $100 or less cooler that can bring that i5-4690K up to 4.8Ghz, maybe even 5?!
Honestly I haven't done much research but from what I've been reading... Your best bet is either a Noctua NHD-14 Air cooler or an Corsair H100i Extreme Series (both 100 or less). However, if you plan to overclock THAT MUCH, you may want to build a custom water cooling solution, because closed loop solutions will most likely not get your desired overclock. Even if it does, your running your CPU on the edge. The max I would suggest with air cooling is about 4.4-4.5ghz and closed loop water cooling is about 4.6-4.7. However, with whatever you plan to do, I would suggest using some type of Turbo Core tech with it once you have a stable OC. For example, do you really need to run your CPU at 5Ghz constant, or can you run it at 4.6Ghz on idle and 5Ghz under full load? It would definitely save a little power and increase longevity.
Also, think about it before you overclock. If you are gaming, try stepping 100mhz each time and prime95 it. If it's stable, play the most intensive game you have. If you are satisfied with the performance, then leave it at that. There is no reason other than bragging rights to overclock a CPU that high when a lower clock could run your desired application at desired settings and reduce power consumption as compared to a higher clock and increase how long your CPU will last.
Also keep in mind that the higher you overclock, the more chance for instability. Your CPU is one of the best out right now for single threaded gaming, so perhaps you may need to ramp it up to 4Ghz. I honestly do not know because I've never used it, but what I do know is saving money and time is the best thing to do.