Most gun "safes" on the market today will thwart a smash and grab type of attack. Find one large enough to fit your needs, don't put it in plain sight and bolt it down if you can. The strength of the gun safes on the market today is in the door. Nearly all can have a nice door cut into the side with an angle grinder in a short amount of time so don't buy into the hype of demonstrations with 3 guys with pry bars unable to defeat the door.