The areas you mentioned would be good to treat, but I would certainly make sure you hit the corners. Bass tends to build up and corners, and it is usually the best place to treat bass in small rooms. If its possible, floor to ceiling in the corners would be great. Considering the hard flooring you might also want to look into clouds (that is, panels hanging from the ceiling). Take into account that there aren't only 4 corners in a room, but 12 - if you don't have much floor space, you can always look into hanging panels in the wall-to-ceiling corners of the room.
Also, don't underestimate sub positioning. It can be quite tricky to find a good spot for a sub in a room. I would experiment a lot with that to get the best possible response. After all - at least positioning will only cost you time.