You're looking for a 120mm x 120mm x 38mm fan which can produce at least 120 CFM of airflow and runs on DC 12V. (Source.)

According to a random guy on the internet, the stock fans produce about 60-70dB of noise.

There are various fans you can buy, but they're all pretty similar in terms of noise.

• http://www.newegg.com/Product/Product.aspx?Item=N82E16835213006

You can also buy one that has less airflow, but is much quieter.

• http://www.newegg.com/Product/Product.aspx?Item=N82E16835132022

...or, if you've ever looked at your Hurricane and decided you wanted twice as much airflow, you could install this:

• http://www.newegg.com/Product/Product.aspx?Item=N82E16835706015

  (The product reviews even use the phrase "jet engine.")

This will void your warranty. (Assuming you have one.)

Heres what you need:

• TWO (yes two) equivalent size silent fans (these will do)
• a CPU fan splitter cable (this is good)
• Screwdriver (duh)

Extra points (Optional):

• Drill with metal drill bit
• Zipties

The Fractal Design Silent Series R2 have a noise rating of 18dB and push 66CFM of air.There are cheaper ones as well that push less CFM. Just to be safe I wouldn't cheap out on these, the more CFM the better. NCIX has awesome selection of fans and are always having sales so you might find something even cheaper.

Keep in mind that stock 120 CFM fan will not be operating at max capacity and a push-pull setup like what I am describing will operate at a much higher efficiency rating.

Heres what you wanna do:

• Open up the case
• Replace the front vent fan with one of the new silent fans taking care to orient the fan backwards so the air is pulled out of the machine (use zipties or rubber grommets to reduce vibration)
• If you don't have a drill, jam one in between the radiator blades and the case on the other side, taking care to orient the fan so it is pushing air inside the machine. You can use a piece of rubber/metal/wood (I wouldn't recommend using something plastic)
• Attach both fans together using the splitter cable, then plug the splitter cable into the mainboard or powersupply.
• Reattach case

Extra Points:

• With your Drill, and the case OFF drill 4 holes in the intake side equivalent to the 4 holes on the corner of the fan (try to line it up so the 4 holes are in the center of the radiator fan)
• Line up the fan with the 4 holes and using zip ties, tighten the fan into place taking care to orient the fan properly

*Pro tip: loop the zipties from the fan-side so that the plastic nubs don't stick out and cut the tails off your zip ties for christs sakes!

Voila! you have reduced your 70-90dB monster growl to a 20-25dB kitty purr. Air is pushed into and along the radiator blades by a 66CFM fan and is pulled along and out the other side by another 66CFM fan. Operating temps might be a little higher but nothing to worry about. Also can be used to quietly heat a room (save on heating in the winter).