One of the best sites, if not the best site, for unbiased, objective reviews of home audio subwoofers and subwoofer drivers is Data-Bass.com. Josh Ricci, the site's owner, has developed an extensive list of measurements that he complies on his website for visitors to compare products from various companies. He recently reviewed the XS15se and the XV30Fse.
The XS-15SE offers a lot of bang for the dollar. The driver is a high quality piece in this price range and the enclosure and finish is heavy duty. The engineering and DSP settings also seem to be well applied and thought out. It is one of the few, sealed design, powered subwoofers offered for under $1000 that is both engineered well and has enough headroom for a decent sized room. Based on the measurements and performance metrics alone it compares quite well to other commercial sealed subwoofers at 2x to 3x the price.
The XV-30Fse is a big subwoofer that you are not going to sneak into the room but it easily performs its duty of fulfilling the requirement for a lot of bass headroom with a very reasonable cost. In room substantial output to 16Hz or so should be realized with loads of 20-30Hz power to drive even a large space well. Additionally in the upper bass range from 40-120Hz the XV-30Fse possesses mighty output capability for those instances when you want to forget about running the bass flat and just crank it up with some of your favorite music.