To watercool RDRAM (which is conceivable in a total 'silent' solution ala Bladerunner), you should use a "standard" WB, for example a chipset or GPU model, and put it on a "table" where the legs of the "table" would touch the chips.
That would be fairly enough to cool down rdram, cost only 1 cheap WB and a few copper bits.
Code:
|| ||
+--++--++--+
|waterblock|
+----------+
|I| |I| <-- "legs"
I I
__+I+____+I+_ <- mobo with ram slots