NSXNUT is on the money - but read his post carefully regarding the variables he mentions.
You are correct, for 75% this is fine if you do not track at ambient temps above 85F and especially do not have a CTSC. A 600 rwhp will not overheat the system in street driving even if occasionally you test its power - but take it to the track with an OEM radiator and within the third lap I assure you the needle will be close to red if you are on it. I too had a radiator shield and it worked well for street driving but had to remove it at the track due to overheating (many of us have had this issue and amply discussed in other threads) and this before installing CTSC.
Add to this the age of a radiator and the climatic conditions it has operated in - as in dusty, insect infested freeways ....... then the 25% of street driven owners kick in.
So, like in many such posts, the key in appreciating responses is in defining and delineating the rest of the parameters/variables.