Never, Never blow fans into gear unless you know where it is coming OUT. You can actually trap heat if there is nowhere for the air to go.
Using fans as 'pull thru' is better, in general. Set it on top of the vents on top of the receiver.
A confuser style 4" box fan is nice.....I had one of the back of my Carver Cube and when in use, the amp never even got warm. And that was running near red-line for hours into 5 ohm Magnepan MG-1s.