#1 - Buy a fire SAFE. (some safes are fire and water proof, important IF you live in a low area) Fire safes can work to protect important papers and other valuables from threats other than burglary.
Check. Some of my friends buy "cabinets" that are supposedly secure with locks. But a crow bar and quick jerk is all it would take to open them.
#2 - Buy the biggest SAFE (not cabinet) you can afford. Cabinets offer very little protection to determined burglars and no protection from fire. Buying the biggest safe you can afford keeps you from having to spend the extra $$$ to upgrade later.
Check. Mine is head high and about 3 ft. square. Plenty of room to hold all the guns, plus the crap my wife wants to keep tucking in it. Frankly, I don't give a damn if someone steals my wife's earings.
#3 - BOLT IT DOWN Bolt whatever safe you get to the floor and as many wall studs as possible. If you don't make the effort to seriously attach your safe to your structure/house/slab then all you've really done by locking you guns away is box 'em up for the thieves to put on a hand truck and easily cart away.
Check. A hole in the center of the floor of the safe allows a chain that attaches to a cemented-in anchor in the garage floor to be secured with a lock inside the safe.
#3 - HIDE IT If possible install/secure the safe in a closet or out of the way corner where you can hide or disguise its presence. Advertising you have something valuable enough to warrant a safe and hey its right HERE is not the wisest move.
Check. Mine is in my garage and I built a cheap looking but solid plywood cabinet around it that is kept closed from curious eyes by it's own padlock.
To make the padlock on that cabinet look like it has a simple purpose (other than hiding several $K in guns), there is a sign on the cabinet that says" "Danger - Poisonous Lawn Chemicals - Keep Away".
I've had that safe for more than 30 years, and to this day, not even others in my family know I have it and what's inside. Just me and the wife (and she's more paranoid than I am) know what's in there.
As a side note, I realized a long time ago that the very, very, very best security system is that of
stealth.
You could have a Million in cash in your closet, but if NO ONE knew about it, you wouldn't be much of a target.
Never forget that the casual acquaintances you have might be really impressed by your collection, but the more impressed they are, the sooner they mention it to their kids and then the kids to their high school friends and then the high school friends to their drug dealer friends... you get the picture.
It's sort of like how the plot of "In Cold Blood" unfolded where the repeated and passed on rumors turned out to be false but people died because of them.
My .02...
tell no one other than your friends who have just as much to lose as you and are as aware and paranoid about these things in the same way as you.