Nucleo Pro should help, but I haven't tried it with CS3.
If you're still not pinning your processors at the max, you can try the old trick of rendering to still sequences with multiple instances of AE:
http://generalspecialist.com/2006/08/ae-render-in-background-work-in.asp
You have to render to stills using this technique, with "skip existing files" on. I recommend rendering to stills anyway in case of a crash, since you have no margin for error.
Of course, hide AE or use caps lock so AE doesn't have to refresh the screen.
Hope that helps.