I have the original CM 690 case where I'm using:
- 4 Aerocool Streamliner 140mm fans, 1000 rpm, 40 cfm
- 2 Scythe S-FLex fans, 1600 rpm, 64 cfm
- 1 Cooler Master fan, 1200 rpm, 40 cfm
I use a fan controller to run both S-Flex fans at 1300 rpm for less noise.
- 2 Streamliner fans on the side case, intake air for the video cards
- 2 Streamliner fans on the top of the case, exhausting heated air out the top
- S-Flex fan on the front case; intake air for the drives
- S-Flex fan on the rear case, exhausting heated air
- Cooler Master fan on the bottom of the case, intake air
I tried using an 89cfm fan on the side case at full speed, ~ 2000 rpm, and this caused my highly overclocked N4660GTX temperatures to rise more than 10o (C) while stress testing!!