Here's a tip from an old guy: Before you pour your floor, put 2-inch closed cell foam on the ground underneath it. The concrete becomes a heat sink, and you will never have cold feet - ever. The concrete soaks up the heat and radiates it back into your room instead of constantly drawing up cold ground temps into your house. I have built 3 shop buildings over the years. Each one has this foam treatment under the floors. My current shop has 6-inch concrete over 2-inch foam. It is wonderful! They concrete guys leveled the land, then put construction poly film down, then did whatever reinforcement wire/bar they needed. Then they poured the floor.

I currently don't have a wood stove/fireplace in my house, and oh! how I wish I did. My shop is wood heated though!

You should definitely use foam and a vapour barrier beneath the concrete. See e.g. this video.

The R-value (how well a material resists heat flow) of concrete is pretty crappy compared to foam insulation. See e.g. this table. You want to break the thermal conduction between the concrete and the soil.

Once the concrete is insulated from the soil, it can act as a thermal mass. And on that note, why not build a rocket mass heater? The "Fouch family off grid" channel on youtube has some informative video's about how they built their rocket mass heater, and how well it works.