It's hard to get a variable speed furnace with an output that low (on high stage), but a Trane XV80 can be had that puts out 48,000 BTUs on high. A Rheem modulating furnace
Two stage furnaces would be quieter mainly because they can run on low for most of the time, but be sure that furnace is sized so that the calculated heat load matches the HIGH stage. Otherwise, you've really just bought a very expensive single stage furnace that will only run on low (except when recovering from a setback).
A Rheem modulating furnace can run as low as 40% of it's rated output (versus 66% for a typical 2 stage), so that might also be a reasonable choice.
they are certainly quieter when on low I have the XV80 air handlers and they are very quiet on low, but just as noisy as anything else on high.
If you're having excessive noise problems check for proper mounting of the thing, and you can also purchase rubber feet to put it on or other even more exotic sound deadening stuff to put it on. Also make sure there is a vibration isolator in the ductwork. Or if the duct work is just too small it's going to be noisy as long the the proper amount of airflow is trying to get through.
We have the Carrier 58MPV 060 and I don't even hear it most of the time. Just make sure you also put a 2 stage thermostat in charge of staging, it makes a big difference in that the furnace will run much longer in low stage. With the furnace doing the staging, it will run a MAX of 16 mins on low then kick into high. This is VERY important if you want a quiet furnace.