In the basic home built in about the 1970s, so a great many homes around my area at least (Southern California), about how much stuff can you have running in a room/on a circuit before you should start worry about power?

Say if you have a computer that has 3 HDDs in it, a 24" monitor, printer, a 6.1 surrond sound PC speaker setup (creative 650s), DSL modem, router, 3 lamps, cell phone charger, clock, television.. lol, you get the idea right?

Should I be worried about the load?

Also I know a UPS is a good thing to have in general, because it can save your computer from a surge or power outage, but if you run into problems with how much juice your pulling, would a UPS be able to supplement that at all?