there is a REALLY quiet panaflo (30db) 120mm x 120mm. Check it
out here. this is what i use in this identical case on all pcs i build for friends.
Also, VIBRATIONS cause a lot of noise. try to de-couple the fans from your case chassis, using rubber gromets or the like.. i've seen someone use the tube like that used on the back of a clothes dryer (go look, you'll see), to connect the fan to the front, this eliminates the vibrations, and therefore, the noise from the fan moving the chassis.
hope that helps, i was looking for a picture / link (i believe from arstechnica forums) where somebody posted nice pics of this.