ok, I'm getting these for my system. thermalright has all your passive cooling needs imo.
Thermalright HR-07 Memory Module Cooler (DDR1 & DDR2 / Single & Double Sided) - FrozenCPU.com
I don't think that watercooling your ram would be necessary. these coolers are great, and stackable *you can put them on ram that is side by side just fine* if you get the tall ones and the short ones, and you can even mount a fan to these if you are REALLY worried. next thing, as stated, check other components and airflow. a really good way to do that is with some smoke *like a smoke bomb* by one of your air intakes, watch to see that it gets recycled through all your components