It isn't the number of fans, nor the number of holes in the case that matters. It is all about airflow through your case.
The object of any air cooling system is to get as much cold air into the case, slam into as many objects inside the case as possible, and then exit the case as fast as it came in.
If you are really into the case cooling thing. You might be better off cutting another hole in the side of case. Mount another fan. Have all three fans 80mm fans the same in your case. Same CFM, Size, Speed, etc. Have the two on the side blow air onto your components and have the one in the front and the back draw air out of the case.
See, this way the airflow into and out of the case should be fairly equal. Also you will have the coldest air hitting components and taking the heat energy from them and then exiting the case via the front and the back.
Now your PSU will help to equilize the airflow system but if there are any shortfalls, that is why there are excess holes in your case.
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