What portable heater should I buy?

I live in a Cape Cod and my upstairs gets very warm. I'm looking for a portable heater to heat up my downstairs that is approximately 900 sq ft. Mainly just my living room, but if I could get my whole downstairs it would be great. I'm not sure of electric, propane, radiant, kerosene, etc etc etc. Anyone know of any good models or recommendations? Thanks in advance.