I contacted my insurance company (Travelers) and they said I was already insured up to a certain amount from theft and fire, but only for the cost of my cards (not current value). It was totally inadequate.
But you really can't be compensated for the time you've spent putting your collection together. The safe deposit box is fine if you don't mind being away from your cards. But as I said in the other thread, if you like to be near them as I do, I highly recommend a top quality fire proof safe. Ft. Knox safes are built like, well, Ft. Knox.
http://ftknox.com/