Each computer should have its own circuit.

Why? Computers typically do not take much power.

True, and if that were the only consideration I would agree - monitor and PC
are usually no more power than four or five table lamps. Presently, my
system is running on a multioutlet surge suppressor and UPS and has been for
quite some time. However, I have client data on my primary box, and as I
understand it, the standard in my industry is to isolate the "server(s)"
from other devices (like refrigerators, stereos, etc) as one facet of a
multifaceted approach to safeguarding data. Makes your heart skip a beat
whenever someone in another part of the house starts up the microwave and a
screen with three-quarters-of-a-million records of customer data jumps.