Don't forget, while Copper provides "666x" faster heat transfer then just the water, the performance will be judged by the poorest component not the best, in this case by either the core ->TIM-> IHS application, or the IHS->TIM-> waterblock.

This simplifies the process from "core->TIM-> IHS-> TIM->copper block -> water" down to just "core->water". Though all our theorizing doesn't take away from the fact that the OP is getting crazy good temperatures that none us water or air cooled guys could dream of.