Would it be a waste to use some tower speakers as surrounds? It would be nice to have full range speakers in the back so I wouldn't have to select the size as small where it redirects the bass to the sub. The problems I see is that the cost would usually be more and positioning them would be more difficult since they could be too low and be blocked by furniture, etc... I was thinking of using a higher end tower for the fronts and a lower end version in the same line for rears. Any thoughts?