I made a short test animation using particles simulated in Real Flow, exported to Octane Render for instancing using a little program I made.
The particles are instances, which is the only reason I think why it's possible to have more than a million spheres without my GTX 570 running out of memory.
For a little technical info, my program reads ASCII files created by Real Flow, grabs the positions of all the particles, writes them to a text file for Octane Render to read with a Scatter node, and loads Octane Render with commands to render each frame.
If anyone is interested I could potentially release the application, it would take a lot of time to make user friendly however.
I plan on creating something far better with the same particle rendering. I regret that the scene is a little boring, and the particles don't seem to be even close to touch geometry.