Typical airflow goes front to back, with the side opening being used for direct intake to the CPU.
Sometimes it's suggested that only rear exhaust be tried first -- that way, you don't risk a side to back bypass, and can force some intake air flow over the hard drives, which will typically cool the drives.
Getting a 80mm fan with good airflow and quietness is very hard, perhaps impossible, but using multiple fans can make this easier, and you do what you have to, and sometimes adjust your tastes..
The Zalman 80's aren't bad -- they're inexpensive, easily available; have a non-bothersome noise signature, and only sing at high volumes; can do fairly high volumes; down-volt well, and come supplied with a fixed resistor for doing so. With a Fanmate / other controller, they can usually be tuned for desired flow / noise performance -- tune down until not bothersome; check temps; revise as wanted/needed.
Arctic Cooling Arctic Fan 3's seem to give very good flow / noise. They're deep-well open back exhaust-only designs. The TC version is temperature-controlled; you can short this and take over control with a Fanmate / other controller. Hums a bit, but might not be too bad overall.
Antec Tri-cools might do the job + LED's for you -- I have no direct experience with these myself; other Antec 80's I've tried tend to buzz a bit, and do OK at a distance and at lower voltages, but aren't the best.
Some Silverstones (be careful there, some of them should be in vaccum cleaners only) and Nexus, etc., do silence well, but at very limited air flow.
Would like to hear of any other 80's that do flow without noise and down-volt well, but am not that hopeful.
I expect some of the cheaper "no-name" fans to do well esp. down-volted, but find that the shelves seem to be filled with name-brand / LED fans.
Among these, the Vantec Stealths aren't exactly silent, but do give a silence / flow balance that might be OK for you (low on flow, but not at the Nexus level; not really silent, not at the Nexus level). I'd suggest a pass though -- I think that the Zalman's or some "no-names" might give you more value / money and flexibility overall.