Power: Are you keeping your factory speakers? If so, you don't need to worry about a brand name stereo's power rating. It'll drive your factory speakers just fine. If you plan on replacing your factory speakers, however, look for one of the higher-powered models. (Remember, "CEA compliant" compliant models will have lower RMS power ratings than non-CEA models.)
Preamp outputs: Preamp outputs let you connect external amplifiers to power your speakers or a subwoofer. The number or outputs can vary, but you should have at least one set — the higher the output voltage rating, the cleaner the signal. If you know you will be adding a subwoofer, look for a model with a dedicated subwoofer output — this will allow you to adjust the subwoofer volume independently, rather than using the bass control.
Signal processing: Higher-end stereos have advanced sound porcessors that can decode surround sound formats like Dolby Digital and DTS. Some can also process advanced CODECS such as DVD-Audio.
Display: If you will be listening to MP3 discs or satellite radio, you may want a display that shows the song, album, and artist information without a lot of scrolling. Enhanced graphics make it easier to see the display at a glance and provide you with more information. They also make it easier to control and adjust the stereo. And some displays let you select their color, for a better match to your dash lighting.
Are you planning on expanding your system?
