Floor safes in a concrete slab are what most businesses use to store cash.
Sentry safes are junk, IMO. I have ( had ) one in my warehouse of junk, and in a break in, the thieves had no trouble prying it open, completely ruining it in the process.
Of course it was empty, because it would be crazy to put anything of value in it. Would have loved to have seen their faces - I always get a chuckle when I think about it. They didn't even bother with any of the really valuable stuff there, or were just after cheap safe type stuff. I still keep it there to let any other thieves know they were too late.
I guess you could get it for a bait safe, and put a real one in your slab.