So you've got your computer, your input device, and maybe some specialized keyboard. The only thing you'll need now is some sound system. In the conclusion of this series, we'll take a look at what you use for game sounds. For general gaming purposes, your computer's default sound system, if any, should really do fine. On the other hand, if you're serious about your PvP, you might want to invest in a good headset. If you normally play at home and have the luxury of playing indiscreetly, a great sound system is an awesome thing to have.
Personally, I don't play external background music (e.g., through iTunes) whenever I PvP. It's cool for PvP videos, but it's generally a bad idea. For one thing, music, even the one found in-game, tends to obscure important PvP sounds. In particular, the stealth sound is one of the most important sound effects in World of Warcraft PvP. That sound will often, but not always, precede visual confirmation of a stealthed unit nearby. If only for this reason, I turn up game sounds and lower in-game music to an ambient level.