I agree wholeheartedly w/SB's advice. Read and understand your policy. Know whether you're covered for "replacement cost" or for "actual cash value" and understand the definition of each as stated in your policy. As a general rule, when you own valuables exceeding the limits of your policy, then you need a "personal articles floater". This is in addition to your regular contents protection and requires additional premium. It's often recommended for furs, jewelry, antiques, works of art, etc. Your contents policy may state that it doesn't cover these "special" items and to cover these items a special rider or floater is needed.

I have a personal articles floater (some companies may call it a rider), but it doesn't include my gear. It includes some of my wife's jewelry. Right now, my gear is covered under my contents. As an example of a piece of gear that should be on a rider/add-on/floater addition to your policy, let's say you have a Marantz 10B tuner that goes for $2,500-3,000 (haven't checked the going rate in a couple of years). Actual cash value won't replace it and you would be arguing with the insurance co. from now on over replacement cost and there's no guarantee that you could replace it.

The spreadsheet/inventory is an excellent idea and many companies provide a sample inventory sheet on their websites. With a digital camera, it shouldn't be too difficult to take and store pics as well.