Don’t know about modular safes, but until I lost all my firearms in that boating accident, I kept them in a Liberty Safe (http://www.libertysafe.com/) which weighs about 500 pounds.
No deconstruction of the house was required and I’ve installed it two houses. Fits through standard doorways without any problem. At my current house, the movers were able to put it on a dolly and roll it in into a closet.
The retailers for safes have all kinds of equipment to get a safe into a house, including gadgets that “walk” a safe up or down stairs.
I ordered a catalog. Gander Mountain here in MN sells them.
Worth a look , I suppose, if they haul it in.