First of all, if you’re going to own more guns, than you can carry with you, you need a gun safe.
Unless you live in a big private estate, your neighbors are better than any alarm system, make friends with them and help watch each other’s houses.
Make sure you keep your neighbors informed when you’re going to be out of town.
The best safe is one a thief cannot find.
Use long through deadbolt locks on all exterior doors, with long screws, for the plate that the bolt goes into, and long screws to secure the wood around the metal doors.
While a reinforced door will not stop a thief, it will at least take them two kicks to open the door, thus give you time to get to your gun. And it makes allot of noise that a thief does not want to make, when he has to keep hammering open a door.