I feel for you man. I'm not trying to be a smart@#* when I say this but the value of the ammo taken was probably worth more than some or all of the guns you may own... Why wouldn't you have it in a safe as well?? I hope you catch those bastards!!
Save up and get a quality safe with a good fire rating. If it's going to be on the smaller side, I'd suggest anchoring it so it can't be hauled off. A cheap safe is just that...cheap. Look for the construction aspects, i.e. thickness of shell, door construction( layered or thick plate ) locking...