I have to strongly suggest going with Cupidr17 ideas.
It's really useless to try to fight general heat rise in a case, i.e. blow in cold air at the top or middle.
Draw cold air in at the bottom... let it rise... expell it at the top.
I tried to fight warm air rise in my case... I lost. I had a 120mm fan blowing air from the back right in to the cpu fan, but still I ended up with higher cpu-temps!
My setup is: I left the back pci slots open, had a 80 mm fan far inside PC angled towards the HD-rack, a 120mm expelling air to the back of case right beside the cpu, and the PS also evac's some air. My PS gets mostly cold air from a hole ontop of my case.
So... wise from my attempts I flipped the fan over and expelled the hot cpu air instead and voilá ! 4C lower temps!
Also most of the air into case comes from the openings in the bottom of case
As others have pointed out, drawing air in so close to the powersupply will mean, you'll be sucking some warm air.
One further tip for you Sandrock: Make sure the fan in the front can breathe! It seemed a bit stuffed by the plastic cover and the tiny holes... tiny holes suck.. one big hole will blow!