Talk about over-engineered. I think you'll find that the two case fans near the CPU will be starving/fighting the CPU fan.
ie the CPU fan will have to spin faster than otherwise, to compete.
I think placing a duct over the top of the CPU, at least a partial one, or one with a 180 degree shape to it (half pipe, tapered), should prevent the two case fans from starving the CPU fan too much. ie air flows in from the front, into the top of the CPU, and the case fans exhaust the CPU's and other devices' (hot) air, baffled by the cpu duct so it they draw air from around the sides of the CPU, rather then across it.
A good tinkering exercise...PS: the ducts I've been talking about in these posts are just the middle sections of clear plastic drink bottles, cut up, etc. Not those flexible air-conditioning style ducts. Recycling...