Great recent article on fan placement and the impact on cooling:
http://www.bit-tech.net/hardware/2012/02/10/the-big-cooling-investigation/1
Some tips:
1. Make the PSU intake from the bottom and exhaust out the rear.
2. If you mount a side fan, then make it an intake
3. Make any top fans exhaust.
4. Any front fans as intake.
5. Normally the rear fan is an exhaust, Corsair recommends mounting the H80 on the location of the rear fan and making it an intake to improve cooling efficiency. I have an H80 and tried it both ways....intake had significant cooling performance increase over exhaust. I have my 2 fans on my H80 in a push/pull configuration. Again, don't mount the H80 in one of the top fan mount locations.
6. 140mm fans move more air at lower speeds than 120mm fans...this makes for a more quiet PC. I wouldn't go out and buy 140mm fans to replace 120mm fans, but if I needed to buy more then i'd go with 140mm.
To minimize noise and still get good airflow, I would personally go with this config:
1. One side mount fan as intake
2. Top-Rear fans as intake.
3. H80 in a push/pull intake at the rear fan mount
Be forewarned that the stock fans on the H80 are LOUD at maximum speed - sounds like a jet taking off. I like quiet computing so I got a good fan controller and all os my case fans and my H80 fans are controlled by the fan controller and set at 1000RPM. Blissfully quiet and I still have good cooling for my parts.