You may want to check on the heat pump. Some have a minimum temp they will operate in. I think 35-40 might be as low as you can safely use them. If you don't get colder that would be a great way to go as you get both heat and cool. You would need some duct work but that's not hard. The unit you have the link for needs a compressor and that might be a bit expensive as it's a major component. But overall the idea is a good one.
