I will be moving house some time soon-and therefore my cabinets. Unfortunately my request for a whole gun room was denied!

So I will be taking part of one spare room upstairs in a 15 year old house, I would like to add another safe as I am running out of room, but here lies my problem…..
I need to fit the safes inside a wardrobe (100x58cm). This will be two rifle safes and one ammo safe weighing in at 270 lbs, add rifles and ammo/reloading components the weight could be nearer 450lbs. The safes will sit on a plinth to spread the weight over a slightly larger area, will be sitting on at least two joists running perpendicular to the exterior wall.
Has any one here got a similar set up, experienced any problems etc? Max floor loading I have seen quoted as 31 lbs/sq ft but this at any point across the joist and doesn't take into account the fixings for the safe taking some of the weight.
Don't want to be causing any issues, locating the safe downstairs on the concrete subfloor isn't really possible with the plans we currently have.
Cheers
JM