Adding vents to duct?
You may look into installing a vent in the furnace room if you have one next to that area. This may allow you to draw heat from the furnace room, into your finished basement area, up the stairs to the first floor and back down again. Depends on where the return is and how things are "zoned". 

If you do install on the drywall get as low as possible so the heat sweeps across your comfort area to the nearest return. Heat rises... Install dampers so you can tweak the amount cool feeding into the basement during the summer. Follow the path of airflow and calculate as much as you can. In tools such as Revit (warning: steep learning curve) it is called a load analysis; though, it can be done back of the hand.

If you already have a ducted system, I wouldn't install an electric heater. Nice for a small area such as a desk/bathroom, but do keep in mind how they affect humidity.