at some point, having more surface area / cooling power will not help you. because your cooling power is so great that it's the TIM that is causing the temp difference between ambient and core temp.
lets say you have a soldering iron that is producing heat, is there any difference between dipping it into a 5 gallon bucket of water to cool off the tip vs dipping it into a Olympic sized swimming pool to cool it off? the 5 gallon bucket of water is already overkill for the 20w of heat the soldering iron is capable of producing so having 10,000 times the cooling power wont make a difference.
so going from a 120mm rad to a 240mm rad, you will see a difference, going from a 240mm rad to a 360mm rad, you will see less of a difference. going from a 360mm rad to a 480mm rad, even less, and so on and so forth. there is a diminishing return at some point adding more surface area can not be justified since the benefit is so small and the cost is so high that it's considered idiotic to try. having 3x540mm rads is enough to cool down an automobile.... NOT something you need for a computer
unless you are modding a V8 engine into your computer so you can take your computer to the race track and race it