There's a lot that goes into it, and 9 is a lot, but it doesn't require any sort of super computer. Resolution is the biggest impact on CPU usage. I'm currently running 5 cameras - one 1280x960, three ...

I am utterly amazed at how easy the current crops of wifi cameras are able to be set up...but off the point. Just bought a Foscam 8910W and want it to go motion activated and sent the photos and video ...