Just looked at your other thread, seeing as you're already up and running i wouldnt change it all just to add another rad. New/better fans will be a much better way of improving it. For the price of a new rad/tubing/coolant you could get 3 gentle typhoons to go in your 360mm rad for amazing rad airflow at barely any noise. Easier, bound to be more effective and no need to mess with a loop thats already working fine.
At the end of the day you can add as many radiators as you want, but if you're already overkill on rad space then adding more shows very diminishing returns in terms of dropping temperatures. Better fans will run cooler and quiter though so would be a much better investment.