I QUITE agree with the push-pull Bill; I tested out those little shrouds sold for Black Ice Extremes a while back. I figured it would be reasonable to just use really long threaded posts so I could mount fan and shroud or just fan on either side.
So I have push, pull, and push-pull results for with or without shrouds.
I couldn't even take the noise of 2 100CFM Papst fans at 12V in push-pull. I just couldn't stand to be in the room. Even at 7V (the results above) it was so much louder than a single fan that I wouldnt recommend it. For very little gain...