Today's aftermarket receivers are brimming with exciting, new technologies — but they're not for everyone.

The Delphi SKYFi™ is a popular add-on to a factory system because it provides an incredible array of XM Satellite Radio stations.

Some listeners are satisfied with the radio that came with their vehicle from the dealership. That's because some people drive leased vehicles, and don't want to take apart the dashboard to install a new receiver. Others prefer their current tuner, or just like the feel of their familiar factory stereo.

But even with a factory receiver, you can still enjoy an expansive world of audio options. With a little installation handiwork, you can add the exceptional variety of satellite radio, the convenience of a multi-disc CD changer, the bass impact of a powered subwoofer, and other options that'll keep you glued to your car radio a lot more often than you would have thought. You can even add mobile video without removing your factory radio, or spice up your car's looks with custom car accessories.

Keys to connections
Several accessible connections let you expand the reach of the receiver that came with your car. Here's an overview of each, and how you can make best use of them:

• FM modulation
  FM modulation is an ingenious method of distributing the signal from a source unit (such as a satellite radio tuner or a CD changer) to an unused band on your FM dial. That means any vehicle with an FM radio is ready for an upgrade.
  
  You'll find FM-modulated packages for a lot of services, including CD changers and satellite radio service. The FM modulator can be mounted in your trunk, under a seat, or behind your dash. The signal cable runs from the changer to the FM modulator. Another cable runs from the FM modulator to the antenna input of your radio.
  
  For changers and some satellite radio units, you have to connect power and ground wires, just like you would with a receiver. When you're ready, simply find the appropriate open channel on your FM dial, and start listening to your source unit.
  
  
  
• Factory-compatible CD changers and adapters
  A large number of factory stereos have CD changer controls, but you're not limited to the expensive changers suggested by your dealer. For particular makes and models of vehicles, some manufacturers now make CD changer/adapter packages that simply plug into the rear of your in-dash stereo.
  
  Also, you might be able to find an adapter cable that lets you hook up an aftermarket changer directly to your changer-controlling receiver. The cable connects your changer and stereo. Again, these cables are available only for certain vehicles, but more are being added all the time.
  
  
• Speaker-level inputs
  Speaker-level inputs are a great feature of many amplifiers and amplified subwoofers. They let you use your factory wiring to add the power of an amp or the bass of a subwoofer to your system. They're ideal for factory systems since they mean you won't need an RCA patch cable or a receiver with preamp outputs for your upgraded sound.
  
  Amplifiers and amplified subs have wires for power and ground. For signal, you'll splice into your factory speaker wire (the easiest place is in the trunk when wire leads to rear deck speakers). The power of an amplifier can make a dramatic improvement in any system — and an amplifier/subwoofer combo can help you hear low tones (and feel an impact) that your regular speakers can't deliver.
  
  

  This Delphi vehicle kit includes a cassette adapter, a cigarette lighter power adapter, a cradle, and roof-mount satellite antenna.

• Cassette adapters
  Cassette adapters have long been used to get more music in your car — most CD manufacturers have car kits available so that you can insert a cassette in your dash, draw power from the cigarette lighter, and listen to a portable CD player through your factory system.
  
  Satellite radio manufacturers have followed suit, and using your cassette for a satellite radio hook-up is a quick and convenient way of getting more entertainment in your car. The principle is the same as with portables — you use the cigarette lighter as a power source and insert the satellite radio cassette adapter into your dash. The difference is that you also will need a roof-top satellite radio antenna (plus the subscription service).
  
  
• Auxiliary inputs
  For factory stereos that come with auxiliary inputs (most do not), you can plug in a satellite radio tuner, a portable CD or MP3 player, a MiniDisc player or other source units with one cable (an RCA connection or mini jack).

The Kenwood "WooX" is a powered sub that connects to your factory system.

So what should I hook up?
Your add-ons are most likely to be a function of your listening habits. Once you've had an earful of satellite radio's 100 channels of crystal-clear music, news, sports, and entertainment, you'll find it hard to go back to terrestrial signals. So, if you'd like to listen to satellite radio in your car and home, you might want to consider one of the satellite radio add-on units that use the cassette opening to deliver service. These tuners are portable and easily removed for use in your living room (or even a satellite radio "boombox.")

If you're primarily interested in better sound quality, then an amplifier/subwoofer combination with speaker-level inputs is definitely the way to go. The amp will raise the soundstage in the interior of your car — this can make a fantastic difference in roomy SUVs. The sub will let you hear previously unrevealed bass notes. (Your regular speakers will sound better, too, without straining to reproduce lows outside of their range.)

A CD changer will give you a music library at your fingertips. Add-on CD changers hold six to 12 CDs and let you play CD music without replacing your receiver. You'd be surprised by the quality of the CD signal passing through an FM modulator — even discerning ears are pleased by what they hear.

Many manufacturers also make DVD/CD changers that give you all the benefits of a CD changer, plus the ability to play DVD movies. Installing a custom headrest monitor and an add-on DVD/CD changer (or single disc DVD player) will turn your factory system into a traveling road show.

So the next time you look at that bland factory stereo resting in your dash, remember — you can bring it to life by matching it with the right components.