ServiceSoon, unfortunately there is no good "One Time Payment" for gun insurance that I know of. The best bet I have seen is to get a rider with your home owners insurance. This way if your house in robbed or you have a fire, everything including your guns is covered. Check what you limit is on your homeoners policy is now. There is usually a $1000 or $2000 limit for firearms on a regular homeowner policy, so if you have a small collection you might not need any extra coverage.
I like security systems, as an overall layered defense for your home, however if you live in a real rural area, I like the central monitoring types like ADT, Brinks, and others. Again its a monthy bill, but at least if someone breaks in you have a call going out to 911, instead of just a siren.