Try moving one or two of Your fans to the pushing side of the rad (lots of work just for checking out, but if You´re *really* curious nothing beats it) and check out how it affects Your CPU temp.
Add a shroud to the pushing fan to decrease the effect of dead spot.
Good hunting.
I could throw myself into a discussion about how more fans will help eachother overcoming the flow restriction through the rad, but since I don´t know jack shit about it I´ll spare You my BS.

regards
Mikael S.