Hi jimbo, think of your upstairs as a balloon or a sealed box.. you are trying to inflate the box with hot air,, a sealed box can only take so much air untill it reaches a max pressure point. excess air must be allowed out of the box before new air can get into the box.
You have to think like a HVAC [heating /ventilation/air conditioning] installer.. You cannot force hot air into the upstairs with out removing some of the cool air from the same part of the house.. You must create a circulation loop.. ALL properly installed furnaces have a cold air return ductwork. or they don't work very well.
Right now, you may have a warm basement, but where is that heat coming from??? Is it radiant heat from the furnace?? or is there a doorway from the upstairs open letting air from upstairs into the basement?? Either way you will have a much more efficient furnace with a cold air return hooked to the fan/filter intake of the coal furnace..