One of the newest technologies to affect changes in driving is the advent of portable in-car GPS receivers.  There a bevy of options included in these products, and many different manufacturers make them.  Below are three models of GPS units from the Garmin company.  Global Phoenix's eBay online store has these three models, plus more.  Any of these are good buys, you just need to know what would suit you the best.  This guide will show you what the differences are between these three models, as well as define some of the features included in each GPS unit.

StreetPilot Series C GPS:
   Affordable navigation for any car and any driver. Color touchscreen, automatic routing, voice guidance, address look-up, 2D or 3D maps, SD card slot. Great for someone looking for a good entry level GPS to get them around.

Nuvi series GPS:
Sleek personal travel assistant for traveling. Color touchscreen, automatic routing, voice guidance, address look-up, 2D or 3D maps, anti-theft feature, travel kit, picture viewer, SD card slot. More portable and more added features such as MP3 and audiobook players,and Bluetooth for hands free calling.

Streetpilot Series  7000:
 All the features of the C series Plus much much more.Get big-time mapping and advanced navigation features for your RV, van or truck, 7-inch touch screen display plus XM radio and traffic alerts in select cities (with subscription).

Basic features to familiarize yourself with are:

• SD/CF card slot :   Does the unit have an SD or CF card slot so that you can upload more data as well as fill the card with MP3's and JPEG's for use during in transit.  (Some models do not have JPEG or MP3 playback ability.)
• 3-D/Bird's-Eye-View Mapping:    Most GPS units have the ability to display maps/directions using bird's-eye-view and 3-D imagery.  These are very useful for seeing getting a sense of the general topography of a region, or seeing what other streets/landmarks are in your immediate area.  Think of it like looking down on a map, but closer, and with an automatic scrolling movement.
• BlueTooth Compatibility:   Many people's personal phones use BlueTooth, and today's GPS unit's, for the right price, feature ways to run your phone calls through your GPS unit.  This is safer, because you won't be fumbling for a small cell phone while you drive.  This feature comes standard on GPS units that have voice-activated controls.  It may be pricey, but it's well worth it.
• Screen Size:    Depending on what kind of car you drive, how good your eye-sight is, and how you have to control the functions of your GPS, screen size can make a big difference.  The car-GPS units don't have small screens per se,  but an inch or two can make a big difference.  You should never go below 3.5" for any GPS unit that has a touchscreen.
• Pre-loaded Data:   This includes maps, as well as POI's.  POI stands for Point Of Interest.  The more of these you have already programmed it, the less work you have to do later.  Prices vary depending on how many POI's are already included in your GPS, but the more the merrier.  Also maps can be pre-loaded too.  Some GPS units only have maps of the U.S., others may include South America and Europe.

  Garmin doesn't offer all the bells and whistles that competing companies do.  This is because when it comes to GPS receivers, Garmin takes their products very seriously and doesn't rely on fancy throw-away features to sell their product.  These machines are for people who are taking GPS seriously, and not using it for fun on day trips around town.  The Garmin GPS line comes chock-full of maps, waypoints, POI's and other data you would need to have a complete atlas inside your GPS.  Other companies might kindly include US/Canada maps, but Garmin makes downloadable maps of North America, South America, Europe, Australia, Middle East and South Africa ready for quick inclusion into your GPS unit. 
The StreetPilot series doesn't rely on internal data storage as much as other GPS units might.  So that your GPS unit will work faster and more efficiently, using SD or CF cards will help keep extraneous data from clogging up your models' processor.  Also you can streamline the information to suit your needs on a particular trip, rather than scrolling through all the minutiae sometimes included on other GPS units' memories.
But, since Garmin doesn't like to leave anyone out of the game, their nüvi series has MP3 players, JPEG viewers and other such features to please any potential customer.  That does not mean the nüvi series doesn't perform well.  On the contrary, the nüvi series from Garmin has quick processing speeds and a lot of memory as well as an SD card slot.  It also comes with a remote, so if you're driving a large SUV and don't want to reach halfway across your car to activate the touchscreen, just use you handy remote control!
Check the chart, see which models have which features and then find decide which model is right for you!
Feel free to check out our online ebay store and get all the information on our available products and prices.  There are a lot of details about the products listed above that weren't covered, so go browse around and get the full picture!