In my experience 2 subs are better than one. They must be identical and in many cases should be placed at the near the midpoints of the room to help control room modes. They are difficult to set up without a tech with the proper equipment to help you,otherwise the placement is really by chance and you probably will not get the most for the money. That being said, properly setup stereo subs sound awesome indeed.
Good listening,
Sgr
Good listening,
Sgr