I read what you posted and figured you might not know about rad boxes.
http://www.swiftnets.com/products/MCB-120.asp
If you only have a 80mm rear exhaust fan you can use one of these to place a 120mm radiator externally. Other than that you are on the right path.
http://www.swiftnets.com/products/MCB-120.asp
If you only have a 80mm rear exhaust fan you can use one of these to place a 120mm radiator externally. Other than that you are on the right path.

