An all-in-one system makes it easier to enhance your TV audio.

Even the priciest high-definition TV can’t fully convey the digital multichannel surround sound of DVD movies and HDTV programs.

To achieve that, you have two basic choices: You can buy components and assemble your own system, or you can opt for a home-theater-in-a-box (HTIB) system.

Buying separate components can be time-consuming and expensive, and connecting them can be a challenge. You can avoid some of the hassle by buying a prepackaged system that combines a receiver with a set of matched speakers and often a DVD player. The package will cost less than building your own system from scratch. Unless you’re a serious music listener, you’ll probably find the functionality and sound quality to be just fine. But these systems typically have less power and fewer features than separate components and usually don’t let you add or replace speakers.

Most home-theater packages include a receiver that can decode 5.1 digital-audio soundtracks, five compact speakers—two front, one center, and two surround speakers for the rear—and a subwoofer that have been matched for sound.

Some systems use two additional rear speakers to further enhance the surround experience. Some packages come with wireless surround speakers or speakers with flat-profile styling to complement a flat-panel TV. You get all the cables and wiring you need, usually color-coded or labeled for easy setup.

Most systems include a progressive-scan DVD player, either built into the receiver or as a separate component, and a powered subwoofer. A few bundle in a VCR as well. Price: $50 to $1,500 for typical systems; $2,000 or more for systems aimed at audiophiles. Panasonic and Sony are among the best-selling brands in the market.

Other systems save space and simplify installation by using only two or three speakers plus a subwoofer. Those create a surroundlike effect, not true surround. Price: $250 to $600.

If space and simplicity are paramount, there are also thin, 40-inch-long sound bars, which hang on the wall near the TV. Those have few wires to connect and none to cross the room. Speaker arrangement or electronic techniques are used to emulate surround sound. Price: $600 to $800.

The receivers in home-theater-in-a-box systems tend to be more basic than stand-alone models. They usually include both Dolby Digital and DTS decoders for handling the surround-sound track when playing a DVD. Controls should be easy to use. Look for a front panel with displays and controls grouped by function and labeled clearly. An onscreen display lets you control the receiver by the television screen.

Switched AC outlets let you plug in other components and turn on the whole system with one button. The receivers have about 20 or more presets you can use for AM and FM stations. Most receivers also offer a sleep timer, which turns them on or off at a preset time. Remote controls are most useful when they have clear labels and color-coded buttons grouped by function. A universal remote can control a number of devices.

An HDMI or component-video output on the receiver that can connect to the TV allows for HD signals if you switch video signals through your receiver. For standard definition, you can also use an S-video output, or a composite-video connection.

Those connections let you pipe signals from an external DVD player, a camcorder, or cable or satellite boxes through the system. Any player that you might want to connect will need the same digital-audio connections, either optical or coaxial, as those of the receiver. And if you want to make occasional connections—perhaps for a camcorder or an MP3 player—you’ll find front-panel inputs handy.

DSP (for digital-signal processor) modes use digital circuitry to duplicate the sound effect of, say, a concert hall. Each mode represents a different listening environment. A bass-boost switch amplifies the deepest sounds.

A subwoofer can be powered or unpowered. Either type will do the job, but a powered subwoofer often provides more control over bass.

An integrated DVD player, available with some models, typically has fewer features than does a stand-alone DVD player. Features to expect are track programmability (more useful for playing CDs than DVDs), track repeat, and disc repeat. If you want more features, a stand-alone DVD player might be the wiser choice.

Decide whether you want a DVD player. If not, you could save money by buying a system without one. If you want a DVD player in the bundle, consider whether you need a multidisc model that will provide uninterrupted play of CDs and DVDs, or if a single-disc player will do. All the DVD-equipped systems we’ve tested have a progressive-scan player. These offer regular DVD picture quality with a conventional TV but can deliver a smoother image when used with a high-definition TV. Some DVD players can play multichannel DVD-Audio and SACD music discs in their original, high-resolution format.

Do you want a separate DVD player or one integrated with a receiver? Systems that integrate the DVD player and the receiver in one box tend to offer a bit less functionality and fewer connections than those that have two separate components. Integrated units are somewhat simpler to set up, but they might not allow you to connect video devices other than a TV to the receiver.

Make sure there are enough inputs. You might want to route video as well as audio signals through your receiver so you can easily switch among sources such as a VCR, cable or satellite box, and DVR.

Consider which devices you’ll want to channel through the home-theater unit and which you can hook up directly to the TV. Be sure you have enough of the appropriate inputs and outputs.

For instance, you’ll need an HDMI or component-video input to feed high-definition signals from a cable or satellite box or enhanced-definition signals from a progressive-scan DVD player through a receiver to your TV.

Each type of connection is capable of conveying a different level of video quality. S-video, component-video, and HDMI connections should give you better picture quality from your DVD player than a composite-video hookup.

With audio inputs, you’ll need a digital-audio input for decoding the digital audio from your DVD player, digital-cable box, or satellite receiver. Make sure the input on the home-theater system matches the output on the other device. Some of these units have an optical digital-audio output, while others have a coaxial digital-audio output. (An HDMI connection carries the audio along with video in one cable.)

Look for front-panel inputs on the receiver if you will be making temporary connections—for example, from a camcorder or a game system—and your TV doesn’t have front-panel inputs.

Some systems have a connection for an iPod or a USB port for connecting other audio or video devices.

Get features that suit your needs. With any system, you can be assured of such basics as AM/FM tuners, Dolby Digital and DTS surround-sound support, and enough speakers for at least a 5.1 surround setup.

A few models offer newer Dolby and DTS surround formats that process 6.1 or 7.1 channels, which support an additional one or two rear-surround speakers, respectively. Those formats still aren’t widely used in movies but could become more common in the future.

Some systems now include an integrated XM satellite-radio tuner, or a minijack or USB port for connecting portable media player/memory devices so you can listen to your music or view photos or videos through your system.

Extras such as switched AC outlets are less common than on component receivers, so make sure a system has what you want.

An onscreen display is handy for setting up and adjusting functions using the TV screen rather than a small display on the console.

Among our tested systems, only those with a DVD player integrated with the receiver had an onscreen display.

Also consider the maker’s warranty. Some manufacturers provide 24 months of coverage, rather than 12 months, on some models.