Nahh, that wasn't it.
It was 2 pc's, side by side. The demo was the same demo used in the launch of the 6800 and this E3 presentation. Though one system had a single 6800 in it and the other had SLi working. The demo was launched at the same time on both machines and finished a lot earlier on the machine using SLi.
It was a very awesome sight. The person wasn't allowed to show the FPS, but it did run a great deal faster on the SLi machine.
If anyone knows of this video, it would be helpful. Thanks.