A home theater in a box (HTIB) is the ideal solution for small rooms. Most models combine a 5.1-speaker package and an A/V receiver with a built-in DVD player, but if you already have a player or want to stick with videotapes, buy one of the more basic HTIBs that omits the DVD deck. Don't sweat the low power-amp ratings on these HTIBs: filling tiny rooms with sound isn't very taxing--just don't expect massive loudness capability from an HTIB.

For these larger rooms, you have two options: buy an upmarket HTIB or pick out an A/V receiver, a separate DVD player, and a 5.1-speaker ensemble. If you opt for the HTIB, steer clear of kits with tiny satellite speakers; you want 3-inch or larger woofers and a 7-inch or larger sub.

Rather not deal with five satellites and their tangle of wires? Check out one of the new wave of virtual surround HTIBs. Then again, more-demanding listeners should stick with separate components. These systems offer greater flexibility along with higher performance, and you can buy a speaker package that matches your decor and your sonic needs.

If you're lucky enough to have a large room, we strongly recommend selecting one of the better A/V receivers and a large satellite/subwoofer package or a carefully assembled group of speakers. The main/front speakers should have at least one 4.5-inch woofer; floor-standing models are the way to go if you want to play the system at fairly loud levels. Big rooms soak up a lot of bass, so you'll also need a hefty sub; look for a model with at least one 10-inch woofer, powered by a minimum of 150 watts.

With all of that space to fill, it might make sense to purchase an EX/DTS-ES receiver. These 6.1- and 7.1-channel models add one or two extra rear-surround channels over the standard 5.1 array, creating a truly enveloping soundstage in large rooms (see CNET's surround sound buying guide for more details). High-quality HTIBs may be acceptable in large spaces, but you'll sacrifice loudness and dynamic range potential.