If you was to have a gaming pc with vents but no fans, a graphics card and an air cpu cooler you could experience some thermal throttling. If you was to add 2x120mm fans in the front, and in the top and also one 120mm at the back you are likely to see a difference of 5-15 degrees Celsius drop in your gpu and similar in your cpu. If you spend £50/$70 on 5 good fans, you will not regret it!!!!Please do it