Stylish fullscreen smoke effect

I’m trying to create a smoke effect that will run in background of a microsite portal. I needs to be pretty big compared to the use we see everywhere of particle smoke effects usign PNG or flash 8 filters.

Here’s what I came with so far playing with some flash 8 filters but the solution still doesn’t perform well enough, especially when we add the other div layers over the animation. I car emore about style that realism, that’s why I like this approach, witch let me used a prerendered image for my smoke texture.

http://allez-hop.com/dev/HEI007

Anyone have some techniques or approach to suggest that could make this project possible? The way it is right now, almost no computer will be able to run it at a decent framerate. I added a detection that stop the animation if the computer canot run it at more than 10fps so you may see nothing moving there!