It depends on the type of media that you are trying to protect.
Floppies, tape cartridges, vcr tapes, etc. are much more succeptable to heat damage than CD/DVD media or USB drives. 
Sentry rated for digital media (low temp) A large number of their safes are rated for CD/DVD storage for 1/2  hour. 
Sentry household fire safes (high temp. digital media)  Sentry product testing descriptions Sam's Clubs currently have a chest size (about 15" w, d & h) for about $50.