As the PC has evolved from a plain computer to an entertainment
center, the sound quality it produces has become an important consideration.
Most PCs come equipped with motherboards that have integrated sound chips that provide connectors for speakers, a headphone and line-in. Having an integrated sound card means that a separate sound card is not required.
A set of speakers is also part of the standard PC package. They can be the stand-alone type or the type that are integrated into the sides of your monitor. They are usually of low to mid grade quality.
Recommendation:
For everyday use the standard set up described above is sufficient.
If you're an audiophile, a music producer or a game player who wants the latest surround sound effects, then a Sound Blaster card from Creative Labs or a Turtle Beach card from SantaCruz is what you would install in your PC.
When combined with a good set of speakers your PC can create very high quality audio. Logitech, Creative Labs and Altec Lansing make speakers designed for PCs.
To add a full, rich bass sound get a three-speaker system that includes a woofer speaker along with the left and right stereo speakers. If you want to use your PC to watch movies then go with a five-speaker system that provides full, home theater surround sound.