I am currently using a subwoofer from an Onkyo HTS-650 home theater system. It is an 8-inch, 150 watt sub. Would a Energy XL-S8 XL S8 100 watt be an improvement over my current Onkyo? And if so, how much? My room dimensions are 20 feet x 20 feet. The room is a square, with 4 complete walls.