No, those little $25 fans won't do shit, prolly not even enough for an intake! When you look for an "in line fan" you want something more like this: (Active Air 400 CFM 6")
HydroFarm: Active Air 6? In-Line Duct Fan 400 CFM [eco-5600B] - Fans, Blowers & Ducting - Environmental Control - Discount Specialty Farm, Greenhouse & Garden Supply Store - Horticulture Source

Don't think that's even an expensive one! As decent fans go this is about the most inexpensive one you'll get away with. That is not to say I hunted for the best price on this link so shop around. This is not a cheap hobby.

Note the below pix are not in scale as they are both 6" openings. Notice the big difference in construction AND CFM's. What's better, 140 CFM or 400? I rest my case potato face. No offense plz, just fun'in witcha. Join my fan club! :giggity::giggity::giggity::giggity::giggity: