I don't know how far you want to go cooling, but I am sure you can grab a watercooling setup that will help you with your needs.
If you want to go very extreme with cooling, then I'd suggest nabbing the vapochill case cooler, which will cool all the components in your case, including both CPUs, probably all to below 0, sometiems as low as -40 temperatures. This also allows you to overclock as much as possible, though I have not heard anyone talking about overclocking an opteron yet, though..
www.vapochill.com