All home theater systems require a good subwoofer, and athena TECHNOLOGIES™ makes models to suit any room. The most important factor in choosing your subwoofer is the size of your room. Larger rooms require a subwoofer that can fill the extra volume of space. Both the AS-P300 and AS-P400 have identical features, controls, and input / output jacks. The difference between them is the AS-P400 is a 10" woofer platform in a larger enclosure, which will ensure lower frequency response, and louder output levels. This makes it suitable for use in larger rooms. Both feature athena's exclusive SCT Control, which simplifies the set up procedure. For details, select a model and read further!