Summary: I've had my Hsu STF-1 for six months now, and I use it daily. I purchased it directly from Hsuresearch.com. Before this, I had a Sony SA-W2500 (basically, a sloppy, weak powered woofer). Realistically, this is my first subwoofer. A "true" subwoofer, as the company calls it. I listen mostly to music, but also movies/TV. It has given me the stereo I've always dreamed of, and my main speakers aren't even expensive!
Summary: ...especially if you're in a smallish room, say 10x14 or so. Hsu has a host of bigger and more powerful models at their website (hsuresearch dot com) for bigger bass appetites and bigger rooms. As an internet-direct manufacturer they and SVS offer amazing bang for the buck, positively annihilating the store-bought brands like Klipsch, Polk, Infinity, Sony (gag!) and Bose (gag! choke! cough!). And with their liberal return policies you have nothing to lose really.
Summary: Subwoofers enchance any tv/movie watching experience at home but the Hsu subwoofer in particular is superb. No distortion, not overly sensitive but it still picks up the deep sounds you want to capture in your living room. I'm impressed by the subtleties it eminates; it picks up bass beautifully in parts of movies I've been watching all my life and didn't know had this undertone.
Summary: From what I gathered after intensive (obsessive) research - there are five good makers of subwoofers. Hsu and SVS are the most highly recommended under $1000, but there are other good ones. The STF-1 is the Hsu Research lowest priced sub and is superb. The STF-2 is even more highly recommended (goes lower but is bigger). Both were more than I thought I needed.