20x15x16 is 4800 cft. That's a pretty big space to fill up IMO. If there would be any way you could go with towers, I would go that route, plus they would be already there for your next house.
While 80W is generally fine, your room is pretty big in volume and 14ft from the speakers is a pretty good distance so what might be considered moderate to loud volume might require quite a bit more power than in a smaller room and the listening position closer to the speakers. The best thing is for you to try it first and then decide if it is enough.
