I used to get a good rate from my house insurance company, by declaring the gear in detail and then adding them as just another few items covered under 'personal possessions away from home '.
The aforementioned idea of photographing and logging the details of each item really gives added peace of mind too.
Don't forget to list / photograph your stock of spare valves, speakers and cables / pedals too, as it's amazing how their value can quickly add up. Perhaps this later consideration applies more to house based damage / theft, but when I added up my 'spares' - it would have been cheaper to replace if the thieves had 'just' stolen a guitar off of me !
