Are you looking for high output fans or a bunch of quite fans. Personally I would take more quite fans over the smaller jet engines you can come across.
Yes you are correct about making the top fan an exhaust. That fan spot has the nickname the "blowhole", you know, kinda like a whale.
The coolermaster 10dbA silent 120's are awesome. Only $10 for the pair and they are SILENT.
Thanks Apokolipse for recommending those.