Hi freesey,
Don't waste your money on the power "outlet" or conditioner. It won't do anything to correct the problem. The initial current draw from a furnace motor, washing machine, refrigerator or air conditioner is substantial, and, as you correctly diagnosed, they should be wired to separate circuits and fuses in your home.
The voltage/current sag is significant enough that your computer monitor and receiver essentially become unstable--almost like quickly turning them off and on again. I'm not a licensed electrician, but you need one. Usually a washer and electric dryer are wired to dedicated circuits (they were in my house in Toronto).
You could run an extension cord from somewhere else in the house from an outlet that isn't on the same circuit as the hungry appliances and use that to power your receiver and computer. By the way the pops or thumps won't damage your receiver or speakers. The power supply to your home may need to be upgraded as well to avoid the current/voltage drops when the appliances kick in.
Best to get an electrician. The rip-off power "conditioners" for audio purposes should be avoided, but a surge suppressor for a computer is okay.
Regards,
