I thought i had read an article before about this, but the cell can outperform GPUs by it self. When you put it with its on GPU, it makes it have the ability to render very high end graphics.
http://www.gametomorrow.com/blog/index.php/2005/11/30/gpus-vs-cell/
It just that people don't know how to get that kind of performance out of the cell just yet







