This is pretty much what I am using. My fans are going to be Blue LED but you get the idea.
You can also get 120 MM models on e-bay cheaply.
I am not saying this is an easy project, but if you can solder and figure out wiring in general you can do lots of interesting things.
I turned 3 clip on LED lights into reading lights. They are 3 LED models and cost about $3 a piece. I added in a 480 Ohm resistor to each to covert them to 12V and a wiring pigtail. They shed lots of light in a narrow beam and cost a lot less then any other reading light I have found.
I do agree that you have to watch out with the PC fans. The high speed ones are really noisy. The ones I have are what I would call a mid-range speed fan. Just a hum, not a whine.
Now that I think about it.. I could just use a rheostat instead of a switch. Then I could control the speed of the fans...