Furnaces: pretty much any brand will do when looking at 95% efficiency models and above. The various brands all have there strengths and weaknesses in terms of breakage. You will be looking at major brand names as generic furnace names typically do not make higher end furnaces. Higher end furnaces come with more things. More things eventually wear and break. You won't find a 95% efficiency furnace with "less" things. All brands break... some of which can be tied to improper / lack of maintenance / improper installation (often blamed on brand), or a combination of all 3. The notion that you just put it in and forget about it? I think that came from the thought that if it's not broke don't fix it. But if you stopped maintaining your body (taking a shower etc) well? You'd start smelling like a goat.

People want to be told what they want to hear... it's called sales 101. Everyone has a shiny new mouse trap to sell you.

Humidifier: this is where you'll likely spend, spend, spend and spend some more. Because maintenance and how these appliances operate. Running water thru something and keeping it operational has it's challenges. (it won't work without water and water creates maintenance issues faster than you can say "osmosis".

I think first is to determine whether your source of energy is to be oil or propane or natural gas. They have their pros and cons, although I am not aware of any oil furnace that reaches an actual 95% thermal efficiency (perhaps combustion efficiency). Oil would be less expensive per BTU than propane, and is safer, but natural gas may, depending on location, be the lowest cost. Only oil and propane make one relatively independent, at least for several weeks, of the external world, depending on the volume allocated to storage. Oil storage should be inside in cold environments. Propane must be outside and distant.

What is the distribution system of your home, including the details of this in-floor radiant system that if it is hydronic; what is the diameter, length & spacing of the tubing?

I doubt you will achieve 95% efficiency with any gas furnace at an altitude of 6000ft. You also have to be very mindful of indoor air quality particularly at higher altitude - carbon dioxide and carbon-monoxide.

IMPO

SR

Is your existing furnace a single unit for all 6000 sq ft?

"You also have to be very mindful of indoor air quality particularly at higher altitude - carbon dioxide and carbon-monoxide."

Are you suggesting that there's any risk at all from equipment that's properly installed by a competent contractor following accepted standards and guidelines, including of course attention to insure the equipment is properly and appropriately vented and also isolated from indoor living spaces?

Miscategorized -- this is not a kitchen Appliances question.

"Miscategorized -- this is not a kitchen Appliances question."

Quite common on Houzz - you can have the same post in multiple subfora. This one appears to have been placed in both kitchen appliances and HVAC. I think it's something to do with how you set up your preferences(?!)