I have 2x 2oomm top and front fans with a rear 120 45 cfm exhaust being a fanaholic I want more case 1 add a 100 cfm exhaust cas2 add a 100 cfm exhaust and a spot cooler on nb case 3 spend a lot replace side panel with haf 912 add a 140 100 cfm intake fan is this overkill I am running at stoc
With so many fans, you can opt for slower fans to reduce noise levels. I leave my PC "naked" so it has this huge fan blowing from above. The only downside - it collects a lot of dust!
A lot of fans is fine, but as Adrian said, if you're going to use that many, making them as silent as possible is the way to go. My priority is reliability at all costs as I build my rigs to last as long as possible, thus I prefer fans with ball bearings or Sintec/Hydrowave type bearing and steel internals with silicone mount dampening. I also aim for slight negative pressure to keep dust out of my system. You can't go wrong with good fan makes like EBM Papst, Panaflo or Sanyo. The last bit I usually do is create "duct zones" where flow is made as lamelar as possible, but this takes a lot of imagination and a basic idea of compressible gas flow.
u might wnat to do some experiment, try turning off some fan and see the temp. compare to full blast of fans.