Protecting that 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.  This type of installation 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.

More excellent information on this subject can be found at http://www.eeel.nist.gov/817/pubs/spd-anthology/files/Surges%20happen!.pdf.