My 2 cents:

When you do add fans, put the intake on the bottom and the exhaust on the top so cool air comes in and hot air goes out. I picked up 2 12v, 120mm fans @ circuit city and they work great for a rubbermaid box I made with old bins for fun (parents got too curious so I trashed it). The fans are $10 each and the 12v chargers are like $12 each off of ebay if you don't have any lying around your house.