I'm curious as to how you used a kitchen cabinet in conjunction with yours. Would you mind going into a little further detail, please? Sounds interesting. Thanks.
I had some extra kitchen cabinets from a kitchen remodel at a friend's home, and so I mounted one of the cabinets directly over the top of the gun cabinet flush against the top of it. The cabinet was used for storage of magazines, cases, etc; but also served as an additional level of security in terms of someone trying to pry the gun cabinet off the wall. The cabinet was mounted in a corner so that prying on one side was not a possibility, and then the bolts on the other side were close enough to the edge of the cabinet that prying there afforded little leverage. So between the bolts and kitchen cabinet it was fastened pretty securely in the room should someone have wanted to just carry the whole cabinet out of the room.
We remodeled the room several years later, and for kicks we decided to try and pry the cabinet out with a big crowbar to see how secure it really was. Surprisingly we were not able to get it out with the crowbar even after substantial effort. Now if we'd wanted to simply pry the door off or cut into it with a reciprocating saw, well that's a different story. But since most residential theft around here is smash and grab, my solution provided short term security until I could save the coin for an actual safe.