Corsair 270R - Case fans question

[Consul]

I really want to improve my case cooling. As of right now, it has one 120mm fan in the front as intake and 120mm in the rear as exhaust.

I want to get 3 140mm fans: 2 for front, 1 for top as I cannot change the one in the back to a 140. The case doesn't support it.

 

My question is: Would there be problems about pressure? I want my case pressure to be as balanced as possible. Any tips?

[CWALD]

you should be fine since you will have 2 in and 2 out. with the size difference you might get a slightly positive pressure but it will be minimal and positive is usually better then negative because dust wont come in through all the cracks, seams, and vents.