For about 10 years I used a Greenlee gang box from Home Depot. I kept all my ammo in it, and had the guns stacked like cordwood (in soft cases) on top. I doubt if I could have gotten 2 more rifles in there, the loaded box had to weigh 600-700 pounds.
I liked the Greenlee for several reasons. It seemed to be heavier steel than the Deltas and Knaacks, it had a shelf across the back for stuff I wanted to have easy access to, and I liked the way that the padlocks were arranged. They swung freely (as opposed to the others, where they're retained in the latch mechanism), which I think would be more of a challenge for a thief to drill.
Also, at 4'W x 2'D x 2'H, it sat in my apartment's dining room for a couple of years, draped with a tablecloth.
Even my hunting friends and the girls I dated never noticed that it was anything but a piece of furniture/
And you can still pick them up for about $300.
While I haven't really looked at them, the Ridgid boxes at HD seem to be very similar,
I know they're not real safes, but I think they're better security than the $150 gun cabinets I've seen.
ETA: When I moved out of my last place, I sold the Greenlee on Craigslist for almost current list price, about $50 more than I paid for it.