I have the SVS 25-31 and it is fantastic. The main difference between the cylinder and box subs, other than shape, is that the cylinder subs are more efficient. That is to say you get more bang for the buck. Box subs tend to take up more floor space for the same performance as a cylinder, but the cylinders look odd to some people and are quite tall. Mine is almost 3 feet. You cannot go wrong with SVS. HSU subs are supposed to be great as well, but I have not heard them.