Well - what do you need 2 more fans to do for you? Do you care about noise? Are you overheating? Or do you just feel like since there's space for them, you better get something to put there?
Mind if I recommend something? Make a single thread for what you want to do, and get all your replies in a single place. Then get your parts, put them together, and enjoy it. Later on figure out how to fix your problems, if you even have any. It's great you're getting interested in all this, but seem to be asking a lot of questions that have already been answered lots of times here, and also and more importantly you're going to go crazy trying to take it all in at once.