High End Equipment Security and Insurance???

It worries me sometimes that someday somebody will break in to my house and take all my Audio stuff. What does everybody do to protect their expensive equipments specially high end audio stuff? Do you write down the serial#? Does the home insurance pay for it if it got stolen? How do you prove to them that you have all these expensive audio stuff? How much do you claim specially for used equipments you bought on the net? I want to hear from you guys.
Thanks,
Royy