Most gaming Computers ARE loud. I could bet 20 bucks that my computer is 2 times louder than yours and I still use it as a desktop. If you want a quite computer, watercooling would be the way to go. You would have to invest in a decent Radiator, some Radiators are louder than a whole case fan set.
But because you want something to quiet down you PC, get one of these:
Fan controllers are great ways to turn down the speed of the fans while your not in heavy gaming situations and such. I have 3 random unknown brand 80mm fans, 2 120mm fans(One is quite silent a S-Flex fan, other is loud) a 140mm PSU fan, a nice 92mm CPU fan, and a 4870 which everyone knows has a monster fan. 100% on that fan it almost hits 6K RPM.
I would recommend one of the following:
This one has 6 control nods, but build quality sometimes lacks in some of the reviews.
This controller has 4 control nods, but build quality is better in some reviews.
If you want to buy new fans, I would have to say, get ones without LED. I found that good fans with good air flow don't have LED's. You could also just pick up a Cold Cathode lights:
Here's some fans that I would recommend to get:
The whole family of S-Flex fans by Scythe are amazing! I have one in the front of my case, I turned it on, didn't hear it at all. It has a fluid baring so its quite as a pin dropping. I highly recommend any of these:
The Kama's are the 80mm and 92mm, the S-Flex are the 120mm but there all amazingly quite and offer great air flow.