Back case rad push or pull?

[exe163]

I am mounting a swifty MCR320 with "radbox" at the back of the case. I wonder which way should I go, push or pull? Note that I have a window right behind the case so I am thinking about air going from back to the case and then exit through front. But then I have another side rad sucking 3x120 amount of air into the base and the max amount of fan I could use for exit is one. Am I worrying too much?

Also should I attach a fan behind the radbox? intake of exhaust?