Hello Lucky and Welcome to the Forum:
It depends on what you are replacing. If you already have a duct systme, it would seem a shame to abandon it; you could use a high efficency heat pump.
The heat in the floor is the most comfortable heat you can get, bar none. It's silent, can even be run off a domestic water heater and lets you go barefoot even in the coldest weather. There are high efficency water boilers also that do a wonderful job. But, what about air conditioning? You can't make that work from pipes in the floor; it requires a seperate system. Sanyo and Mitsubishi have ductless air conditioners that will cool up to 3 good sized rooms and are very high efficency too.