I had time yesterday to connect up 2 more cameras to the system. Oddly enough, the CPU utilization went down! It went from 26% with 1 camera to an astonishingly low 10% with 3 cameras and motion detection on each. I thought since it was dark out by the time I got the cameras connected, there wasn't much CPU used for motion detection on mostly black cameras. But it's bright outside now and the CPU is still low. Maybe with 1 camera, it does motion detection at 30 FPS, but dials it way down with more cameras? Who knows. I was thinking that I would have to reduce the resolution from 640x480 when I added more cameras, but it looks like I'll be able to leave it like that. I also put the server case on its side so the CPU heatsink would have better airflow (it's right under the power supply, which has no fan). That combined with the lower CPU utilization has the CPU temp down to 55°C from 66°C.