I am looking to add 2 120mm fans that push 103 cfm and 2 200mm fans that push 110 cfm and a 140mm fan that pushes 95cfm into my NZXT case that has 2 GTX 580's that tend to run hot when maxxed out. The main reason is that one of them is the tri-fan Gigabyte version that blows some air into the case again. The temps can get into high 70's and my fans will max out at 85% speed. I opened the side of the case to allow additional airflow, but it looks trashy to have the side open. These GPU's generally idle at mid 20's low 30's but I have them OC'd (just for the hell of it) for playing BF3.
Would these 5 additional fans decrease my temps by much (5 C?) or is this a waste of time and money? My cable management is reasonable so that isn't the problem either. My though is that the 140mm fan in front would pull plenty of cool air in, the two lower 120's would pull in cool air from below and be pushed toward the GPU's, the top 200's would pull hot air out of the top, and the side 200 would pull the remaining warm air from the Gigabyte GTX 580 out the side while allowing the GPU's to blow/pull the remaining air as needed.
The big question: Will this decrease my temps by 5 C, noise will not be taken into account.