Not long ago, optioning out a new car was straightforward. If you wanted to add some extra value, comfort and convenience to your ride, you opted for an automatic transmission, cruise control, air conditioning, power steering, power brakes and a decent AM/FM stereo with cassette. If you lived north of the Mason-Dixon Line, you added a rear-window defogger, intermittent wipers, a bigger battery and an engine-block heater to the mix.

Although these options remain popular with consumers, today's car buyers also have a dizzying array of aftermarket accessories to consider such as:

• Multigigabyte in-car navigation.
• DVD entertainment systems.
• Backup cameras.
• Heated or air-conditioned leather seats.
• Performance suspension packages.
• Alloy wheels.
• Satellite radio.
• Intelligent keys.
• In-vehicle Bluetooth technology.

All of this equipment can make life with a new car safer and a lot more fun. But which of these pricey add-ons can help maintain your car's value -- or even increase it -- and which ones can actually diminish the value, making your car less appealing and harder to sell?

Reason to personalize
"The whole notion behind vehicle personalization or customization is to make your vehicle fit you, its owner, like a glove and to really make it meet your individual needs," says Peter MacGillivray, vice president of events and communications at the Specialty Equipment Market Association, or SEMA. MacGillivray says the average U.S. consumer spends about $2,000 on optioning or modifying their vehicle within the first year of purchase.

"Rims (custom wheels) are probably the most popular, easiest and best aftermarket upgrade," says Adam Simms, general manager of Toyota Sunnyvale in Sunnyvale, Calif. "They're an option that not only positively impacts the performance and handling of any vehicle, but they immediately add value as well."

Consumers are also spending increasing sums on mobile electronics that garner a return on investment at selling time.

Aftermarket GPS navigation systems, for example, are popular with today's drivers because they are more flexible and better designed than the systems installed by carmakers, says MacGillivray. Not only do these highly portable "stick-on" units afford you tremendous flexibility -- you can use these units interchangeably among various vehicles -- but they also generally come equipped with such built-in, state-of-the-art features as Bluetooth connectivity and other technologies that make them considerably easier to use and update.