I've been experimenting with running a CM GeminiII with a single fan (over the CPU area) to provide better performance than stock, while remaining quiet.
I had originally outfitted the GeminiII with a Silverstone FN121 hacked to fit over the motherboard's 3-pin connector exclusively. This let the board regulate its speed, but it regulates too well-- half the time, it doesn't start when you cold boot.
In consequence, I replaced it with my other spare 120mm fan-- a Power Logic job rated 83CFM and 2500RPM, which gets very noisy after 1500RPM or so. Although idle gets you 1000-1100RPM, when the Silverstone was actually working, it was delivering like 600RPM at idle, and was obviously quieter.
So I'm thinking-- if I get a fan with PWM control, even if the mainboard drops the speed to 30%, it will run fine. I don't mind if it's a little loud at 100%, because if the cooling is ample, it should rarely, if ever, hit 100, and the stock rear fan is still 1600rpm to drown out anything else.
Now, which fan to get?
I was considering both the Scythe Kama PWM and the Arctic Cooling AF12025PWM -- both are similar in specs, except the AC works out to about a dollar more, is about 2% higher CFM rating, and is claimed to have a MTBF ten times higher than the Scythe. I've been generally satisfied with AC products in the past, but have never used Scythe stuff.
Is there any reason I shouldn't go with the AF12025PWM-- or some third choice I hadn't considered worth buying? I'd like to keep under $15 shipped, because this is an utterly wasteful endeavour, when you think about it-- I have a perfectly good stock cooler sitting on my desk (although, anything that doesn't use those ridiculous turn-while-pushing-and-pulling mounting pins is worth points in my book).