On top of that you have to watch out for an important factor: The power-consumption

6990 is not practical or healthy for a wide use, how to lower the power-consumption, that is the real challenge

I think the power of Gtx580 would be more than enough to launch new-gen consoles with.

What a beast x_X

btw. @ gtx580 and unreal-demo recently shown:

It is unlikely you get this demo since most of it is pre-made stuff, hence it looks like a pre-rendered movie where you can interact less. UE3 is based on baked lighting. It meany you cannot change time of the day and have the same spectacular lighting in the scene. UE 3 is a hybrid engine, it renders some stuff real-time but most of the nice looking assets have pre-baked radiosity maps etc
It will stay just a vision for at least a long time, don't expect those visuals in a complete, interactive and living game.