I disagree fairly strongly in this case with what you said. You need to get the right fan. A well made (Panaflo, or Scythe S-Flex with fluid dynamic bearings) 120mm fan is not loud but will move a lot of air.
Now... couple that with the mobo he's got. Look at the picture:
http://www.gigabyte.com.tw/Products/ViewImage.aspx?ProductID=2288
This board is spring-loaded to get the most from a good "blow-down" cooler like the Thermalright SI-128. The structure of the passive heat pipe chipset coolers on the board are perfect for this setup.
While I agree that big does not always equal loud, to get enough cfm out of a fan in a blowdown design it's going to take a pretty powerfull fan to cool all he wants to cool with just that fan, plus the air you're using has already passed through the cpu cooler which in my opinion is not very efficient. You also run into obstacles of large video cards or cables that can block air flow to those components.
Your suggestion to get a smaller fan(s) to pass air over the passive heat pipe section is problematic and likely cheesy. Where would you mount the smaller fan(s) you speak of? Why would you want to do that when you can get it all with a good simple, solid "blow-down" setup?
By the time you get done with your suggestion, you've spent more in time and money on the Rube Goldberg fan setup and got less performance. And your system board looks hap-hazard, as well.
Since when are 30mm or 40mm fans expensive? They're also small enough to not look cheesy as it wouldn't be larger than the heatsink. I would mount one directly on top (top while case is sitting up, so side if the board is laying horizontally) of the heatsink that attaches to the northbridge. Directly cooling that portion with any leftover heat moving throughout the rest of the passive heat pipe. You'd spend maybe $10 for everything, possible a small amount more for shipping.
http://www.gigabyte.com.tw/Products/ViewImage.aspx?ProductID=2288
Just take a look at the freakin' board. Did you look at it? Just look at it and you'll see that with the passive heat pipe design and voltage regulation modules (VRMs) it is perfect for blow down cooling from the large SI-128.
http://www.gigabyte.com.tw/Products/ViewImage.aspx?ProductID=2288
All the VRMs are cooled along with the chipset heat pipe passive cooling section as well as the memory dimms.
http://www.gigabyte.com.tw/Products/ViewImage.aspx?ProductID=2288
Other boards that have deeply extruded passive heatsinks in close to the CPU are also excellent candidates (like the Intel Bad Axe).
What are you going to do? Pepper the system board with tiny fans that are either to weak or too loud (shrill). Are you going to braid the small fan cables together in a kind of bird's nest motif? Gee, I can't wait (NOT) to see your custom mounting scheme. Will you include a can of Cheese Whiz with the install?
Are you going to use zip ties and dental floss to tie them to different parts of the passive sinks? How will you do the VRMs and the memory dimms? Gee... do you think maybe the crazy placement of small fans will interfere with other parts? How small are they? How cheap are they? How many of these 6cfm wimps will it take to generate the kind of flow you are getting from an ~80CFM 120mm fan?. A single 120mm fan. A single 120mm fan that does the job perfectly.
So if you get four wimpy 6cfm fans at 4.95 each and probably 8.95 shipping (if you go to Newegg), how much is that extra? How much for the labor? How much for the Tylenol you'll need when you get done slapping yourself for stinking up what could have been a clean one fan solution?
Small fans CAN'T by their nature generate the kind of air flow that a large 120mm fan will generate, and the larger fan WILL by its nature be much quieter. Gigabyte put that passive section there to take advantage of blow-down cooling. If you want to disregard their almost perfect placement of the passive fin section and VRMs to take advantage of that type of cooling then I can only wonder why?
Have you looked at the board?
http://www.gigabyte.com.tw/Products/ViewImage.aspx?ProductID=2288