Using Redstone Power 2, I just built a prototype reactor using the same water cooling system I had before. I'm up to 230 EU/tick and a reactor that is starting to resemble a ticking bomb. I have yet to hit the limits of my cooling system. It IS stable, it does NOT heat up past the boiling point of water, and it can be refueled immediately after use. It doesn't require any consumables other than fuel.
Here's a teaser screenshot :
I haven't finalized the design...I think even more power output from a single reactor is possible. Basically we are shoving water into the reactor at high speed and it is boiling, taking the excess heat away with it. This method would work in real life and it is actually how high power commercial reactors are cooled.
We are doing all this in SMP on Bricked Technology, my server. It is on a 4 gigabyte VPS and has a sandybridge CPU, and a lot of mods installed. Go to brickedtechnology.blogspot.com for details. If you log in, I'll show you what I've got.