I would say that you would only have Fan 1 as intake, like Mitch said, creating a nice airflow from the front of the case to the back. Fan 6 should always be outtake, so that it expels hot air coming off of the CPU and GPU. I would also say that 4 should be outtake. Having it blowing in would mean that the air would come and hit the hot part of the motherboard on the other side of the CPU, but then the air would have no where to go. Making it outtake would create a current coming from the edges of the motherboard and exhausting the hot air from the other side of the CPU.