The "Air King" I hear is supposedly the most powerful of the 20" box fans with the most CFMs, but I would still rather have 2 cheap laskos for the price of one of those, or even the fancy "air flex" model that's already made to hold the filters.. I been running the $24 lasko ones with no problems, and think of them as expendable items being that cheap, yet they keep on trucking for years.. They are always available for low price at the stores, and sometimes I find the higher rated furnace filters on clearance sales for around $5 at the same places, depending on the time of year, and I stock up and buy them out. Get like 10+ filters for $50 sometimes which is nice..