So the current setup goes as such.
One 120mm front 1200rpm intake fan
One 120mm 1600rpm back exhaust fan
One 120mm 1600rpm side exhaust fan
One 120mm 1200rpm side intake fan.
I am thinking I should use the 1600rpm fan as a bottom intake fan, and the other side fan as a top exhaust fan. So this will mean 2 intake fans (one bottom, one front) and two exhaust fans (one back, one top).
I have a similar config in my CM690, but I added a 120mm intake fan in the lower 3 5.25" bays, instead of on the bottom (see my Member Configuration) - my CPU temps are 32C-39C - room temp about 68F-70F.
Two 120s intake on front (orig + the one in the lower 5.25 bays, Two 120s exhaust: Rear Back and Top Rear.
To have good cooling it is important to make a wind tunnel in your case, thus according to me, the best way is to have 3 intakes and 3 exhausts...
My case is:
1x120mm (Noctua P12@1300 RPM) on front panel
1x120mm (Scythe SlipStream @1200 RPM) on bottom
1x140mm (Scythe Kaze Maru @500 RPM) on side panel (lower intake for the GPU)
1x120mm (Scythe SlipStream@1200 RPM) on the rear panel
2x120mm (Scythe S-Flex@1200 RPM) on the top panel
I'm quite happy with this setup... I spent quite some time to find the best fan combination (I have maybe 10 spare fans from different manufacturers) to have it as cool as possible while maintaining low noise...