The little cheapo china diesel heaters will be quieter and use less electricity. There is an issue with a clicking noise with the fuel pump unless you can mount the pump somewhere where it cannot be heard. Click is similar to the piezo ignition click of a furnace.
The down side is these heaters will need cleaning from time to time.
The best solution is a small inverter generator, a quiet one, located a few feet away and run an electric heater or two, the 2nd being for basement, and maybe an electric bed warmer.
Otherwise the propane furnace that does have a loud fan is a really good heater. It does use a lot of electricity for the fan, and at zero deg it would run all the time almost, so with long winter nights you would need some amp hours for sure.
The Buddy heaters do just put a lot of moisture into the air and at zero cracking windows is not as ideal as it is at 50.
Eventually anyone will get used to normal sounds. I never did with the heater as I did not run it enough to get used to it, but every night all the time.... well thats your call alone.
I would explore the ear plugs route and try it at home before looking at expensive solutions each with their own downsides...
