Protecting your home theater system from electrical damage is something you should spend a little time working on. When you look for places that harm can come from you need to look at everything that is connected to your system. These include power, telephone, cable, satellite and outdoor speaker wiring.
The single best thing you can do to protect your equipment is to use surge protection devices at the service entrance for power, cable and telephone. Tying these devices as shown below to the same ground will help prevent a surge from entering your home. These devices may need to be installed by a licensed professional. The installation that is shown below and will also help protect all of the electric appliances on these circuits. Protecting your system from local lightening strikes is more difficult and involves preventing wiring acting like an antenna sending surges into your electronics. Information on a quality service entrance surge protector can be downloaded here.
To meet IEEE requirements for sensitive equipment protection secondary surge protection should be provided near those devices like home theater equipment. I like Furman for these applications.
More excellent information on this subject from NIST can be found here.