Memory COOLER

The only worthy WC blocks for memory are custom made. And then it's questionable that the price and hassle is worth it. Decent fan cooling (and there are some nice ones) are fine.
 
DDR2 or 3 with heat spreaders is enough to keep it cool. If you really want the extra cooling, get those RAM fans that clip over the DIMM slots...they run about $18.

You are going to run into flowrate issues with RAM blocks, much like you will with MOSFET blocks and chipset blocks.
 
I would agree with water blocks for memory being a bit of a waste. If your water cooling the rest of setup that removes almost all of the sources that increase the ambient heat in your case so a fan putting some air over you ram should keep the temp hoovering about 2-5 degrees above room temp.
 
why would you need watercooling? i mean the OCZ ReaperX with its rather large cooler is like COLD to the touch no matter how much you stress it...