A TV can't do much by itself. To get true movie sound, you need to supplement it with a home theater system: a digitally friendly amplifier, a large subwoofer, and at least five satellite speakers (or something like Yamaha’s YSP-1000 virtual surround sound set). And your setup will need to include a DVD or Blu-ray player, too.
To turn your TV into something special, you can buy a Home Theater in a Box (HTiB)--which includes the amplifier and the speakers, and sometimes the player as well--or you can collect each component separately. HTiBs generally give you more bang for your buck, but separate components give you more bang, period: They're the higher-end choice.
Here are seven outstanding-for-the-price ways to make your home-movie-viewing experience a whole lot better, categorized by the price of the bundle. Since most of these products have not been reviewed by PC World, I've based my recommendations on my own knowledge of the technology, and on professional and user reviews.