I've only managed to overclock my Pi to 1.3 GHz, but this guy here http://www.overclock.net/t/1404207/extreme-cooled-raspberry-pi got it up to 2.4GHz. Is it the cooling that makes it possible to get up to that high? I couldn't overclock my Pi any more because, if I increased it more, it would crash at startup. Would cooling help with this too? Usually, it seems that you only need cooling to keep the CPU cool as overclocking heats it more then normal, but if it crashes at startup would more cooling actually help?
Extreme overclocking has always required extra cooling or some. Mainly USA PC users have even resorted to water cooled systems.
However, I would suggest, if the stock Pi can't handle whatever you are trying to achieve, chances are you shouldn't be using the Pi.
If you MUST use a Pi, go for the quad core ARM 7 Pi 3B+. (it's said to be 7x times faster)