If you want to keep the floor clear, definitely go with a suspended unit heater. Not being from South Carolina, I looked up your winter conditions and it looks like you do experience temperatures down in the 20's, so you will want to use something that has a fan to get some air movement. With that, I would go with a indirect gas fired suspended unit heater like a Modine Hot Dawg unit. If you don't have gas available, you could always go electric too.
