all i can say is wait for the new opterons with DDR2, then get 2 of them and a board that can support 2.
Also another point......Liquid cooling
Its best to build your own liquid cooling system.......
If you want to liquid cool all your components which may or may not include:
Power Supply(s)*(Not recommended for regular modders)
Other devices with PUs
You may need:
WaterCoil(s)(Ceramic transformer coils with tubes running through)
Digital Monitor(possibly with pressure, multiple temperature, fan speed, coolant replacement calendar, pc control, bios monitor pass through for fan speed andor temp, pump monitor ....)
Pump(Perferably high flow, depending on the components in the system)
You may also want to put an extra radiator between components like between processor 1 and 2.
Liquid cooling power supplies are very rare in computers. Usually you can replace the heatsinks with waterblocks. I've seen someone run coolant through transformer coils.
Also, you'll probably want to use FluidXP+ for coolant because it is a glycerin based non-conducture coolant. Basically, if it spills when your not home it will short out and fry your system. Also, you monitor should be able to shut down your system if there is a leak or failure.