CPU overheating when gaming

Solution
You've kinda half way solved your own question, firstly, you will need a cpu cooler, that's fairly obvious, but as for the watercooling part, no, not unless you'd be willing to spend $150 ish, get a good cpu air cooler, like the noctua dh 14, it offers cooling performance near to a high end watercooler for half the price
You've kinda half way solved your own question, firstly, you will need a cpu cooler, that's fairly obvious, but as for the watercooling part, no, not unless you'd be willing to spend $150 ish, get a good cpu air cooler, like the noctua dh 14, it offers cooling performance near to a high end watercooler for half the price
 
Solution
2 inches will be enough for the cases to draw air from, but just prioritise the front/back of the case for air intake and exhaust as they will be able to take air in better and the exhaust fans at the back will be able to exhaust air out quite well, make sure the back of the case isn't against a wall or something, leave good space between the back of the case and the wall