When it comes to being entertained in your car, there have never been more options available as there are today. So what exactly do you want to do? Look at maps, listen to your MP3 collection, or watch a movie on DVD? If you've got the cash, you can do all of the above. A good place to start when you want to bring your audio dreams to life is a car receiver -- also known as the stereo or head unit. A new receiver can have as many features as you're willing to pay for. Basic receivers provide you with CD playback and often feature colorful graphics. But for a little more, you can get one that plays MP3/WMA files or has an auxiliary input for your music player. In addition, you might also consider a satellite radio receiver for your car. This gives you a lot more audio options, but be mindful of what it costs to