It is true that you will NEVER actually reach a CPU temperature that matches the coldest air temperature measured going into your radiator.
As stated the closer you get to ambient temp the harder it is to get to that point... kind of like a half-life or half-step... if, with every step, you cover half the distance to your goal... you will never reach your goal.
Practiacally speaking, you would get close enough that you wouldn't care about that last 2 to 5 degrees.
The CPUs we are trying to cool have an EXPECTED operating temperature of what... 40° C to 50° C? Average room temperatures in a home are what? 21° C to 25° C? That's a pretty big difference... if you can get your CPU core temperatures down under 35° C you are doing well in my opinion. If you are under 30° C you are doing really well.. in fact I am more than happy with just being under 30° C. If you get under 25° in a room that is 21° C without a peltier or some chilled water setup... you are doing EXTREMELY well.
Again, I was always under the impression that the goal was to keep our CPUs cool under load, especially when we overclock. If they look good and function quietly in addition... then so much the better.
My goal is to have cool and quiet... not just a pressure head that could lift a car and cool a volcano.
