I'm confused
<sarcastic>
All this time I was thinking that when a waterblock gives better temperatures It's because more heat is going into the water.
</sarcastic>
take for example that if a computer creates 100Joules /sec. (100W) in the perfect waterblock all 100W would go into the cooling meduim and make the CPU be at ammient temps. So as waterblock efficientcy increases the water would get warmer.
So in real life say your CPU is 5C above amient, I am guessing that the die of silicon is about 10g (I have no idea about this i am guessing completely) that would mean that it would take 35.5J to raise the temp that much which leaves 64.4 J to go into the water. If the temp was 5C higher then only 29J would go into the water. I hope you get my drift.
But cathar is right that the amount of temp rise is minimal because for every liter of water in the system it takes 4184 Joules to warm it 1C. this would leave a whole lot of time for the water temp to rise and for the rad to remove temps.
I don't mean to sound critical, but I am trying to clear some things up that I feel haven't been.