Well I have a Thermaltake MK-1 case and I have 3 well 4 if you count the push pull fan on the back. One 200mm exhaust out the top and one 120mm at the bottom and the two push pull 120mm out the back.
My intake fans are one 200mm at the top, front, and the side. I have very good air flow. If you have enough air vents then pushing air I feel should be the thing to do.
Because if you are sucking air out then air has to come in so venting hot air in my opinion is better But of course air in and air out is the way to really go. If you can get a exhaust fan above your cards then do it.
I hope that has help you a little. One more thing you could mod your case cut parts out to put in fans. I see it all the time. Just a thought. Cheers