I have a new 20x30 shop and it is a lot more air tight then the old one. I'm trying to keep dust down, what is everyone's thoughts on hanging air filters? How many cfm do I need for this size shop. You can get the 300-400 cfm ones pretty cheap, 1000 cmf take a jump. Most the cheaper ones look exactly the same, is there any real difference between grizzly, jet, wen etc?