Originally posted by: Woofmeister
Assuiming that you are not talking about a home theater PC, purchasing a fan controller for around $30 or so is the easiest and cheapest way to achieve your goal. The fact is that with desktop PCs we really only want quiet when working in 2D applications. When playing games, we can just crank the volume up until it drowns out the sound of our fans. Unless you are doing video editing, or running a ridiculous amount of applications simultaneously, your OC'd processor and video card are only going to start generating lots of heat during games, so that's the only time you will need the added cooling of your fans going full blast. Moreover, because a fan controller will undervolt your fans up until the moment you need to move lots of air, you can make due with lower quality fans and not have to pay the premium for Yate Loons and such (which don't move much air anyway).
I have an Enermax fan controller (which is no longer in production) that controls my three case fans (front intake, rear exhaust and top blowhole exhaust) as well as the 120mm fan on my Scythe Ninja and even the fan on my motherboard. I'm using big honkin
Thermaltake A2018 120mm fans in my case and they blast air like a leaf blower when I set them on full but are quiet as a mouse on the lowest setting on my fan controller. Just make sure you also monitor your temperatures and all will be well. Many fan controllers also have temperature monitor capabilities built in so one device willl resolve both problems.
Outside of that, there's always water cooling!