144Hz - there are two parts to it:
1. CPU - you need a high clocked (over 4GHz) i7 or 6 core i5 to reach over 100FPS in many games.
2. If you want to play on max graphics settings, I'd recommend at least GTX 1070 or 1070Ti.
To be honest, if you have some card at hand, it would be smart to wait a couple of moths for the release of next gen cards.
More performance for less money.
As for cooler, even smaller and cheaper NH-U14s will be comparable or better at cooling with lower noise than 240 AiOs.
Same goes for most decent 60-90$ air coolers from companies like Be Quiet, Cryorig and many others. There are even cheaper coolers from Scythe that do awesome job.
Practical reasons to choose an AiO are usually compact cases with limited CPU cooler height. Some people like the look of AiO.