Replacing the 120mm on a Big Typhoon

[suhmdood]

I'm thinking about replacing the 120mm on the Big Typhoon with a much more powerful fan. Has anyone ever done this and experienced a decent decrease in temperature? If so, what was the cfm of the fan you replaced it with?

 

[smitbret]

How much cooler do you want to go? My CPU's already low 30's at idle and never gets to 40 degrees with the stock Big Typhoon fan.
-Brett