You basically have a hot water system. You use a gas, electric, propane, fuel oil, wood, pellet, or coal boiler, sized for the amount of heat you need, and place it some place out of the way, but have access to the boiler. Example, your garage. Then you have the option of running baseboard radiators, loop pex style tubing under the floor or embedded into the floor, like under the ceramic tile, cast iron radiators or a hot water coil inside a sheet metal box, with a blower fan, called an air handler. The hot water boiler will also handle your domestic hot water heating, year round, eliminating the need for a hot water tank.
Here is an example of such product.
http://freeheatmachine.com/options.html I'm not endorsing any particular product, its just something I found real quick through google to get you an idea.
The nice thing about using a boiler is that you can run the heat anywhere using pipes, which can also be the pex style tubing, under floor joists, between walls, easily. I'm sure a good heating contractor in your area could help you with many options for your specific application, once that you tell them what you are thinking of doing. I found that most heating contractors usually avoid stuff like this, mainly because of the money is made from quick furnace and duct work jobs. Once you know how much radiation that you need for each location, it is pretty straight forward installing the pipe runs and connections. You maybe able to do most of the work yourself, if you are a handy man.
I don't quite know or understand the space limitations that you are dealing with in your house, but this type of system takes up little space to move the heat. The only space you may sacrifice is, if and when, and what kind of hot air handler you want to install. I've seen some really neat stuff out there, small in the wall, small in the floor, and small duct water coils, to very large blower style.
Here are some more links to some interesting options. (broken link removed) (broken link removed) (broken link removed) (broken link removed) (broken link removed)
I hope this helps.