The size isn't the issue there, it is the CFM, if you get a high CFM fan it should do the job
for cooling i am sporting 2 10" HP permacool fans between them both should pull 2500cfm or push 80% of that (2000 CFM) or i can do the alternate thing like Drift freaq said and push/pull 2250 CFM (
http://www.perma-cool.com/Catalog/Cat_page16.html) if you can find a 10" that no shit flows 5000 CFM then you would only need one.