1. How come I see some people use these big 4-6 inch duct fans like these:

http://www.homedepot.com/catalog/productImages/300/35/3593246c-2b26-4086-b95c-bf0cd289f882_300.jpg

and I see others just use two PC case fans like these:

http://c1.neweggimages.com/NeweggImage/ProductImageCompressAll200/35-185-006-02.jpg


Wouldn't that be quite a huge difference?
My projector isn't that huge, so I'm going for the two PC case fans, but it makes me wonder if I'm missing something important by not using big ass fan?


2. What fans are good? 120mm right?
and what CFM should I be going for? I heard anything 100-200 CFM is good, but isn't that loud?


3. What do you call that device I need to buy from Radio Shack that converts the DC volt of the PC fans to an AC current? I need to know what to ask that Radio Shack guy, for he may be as clueless as me.

4. Are buying dust fliters necessary or waste of money? If they are necessary, what do I call it when I buy it from Home Depot?


Thank you for looking at this thread.