Yes you can compare GPS systems on a few websites, Best Buy allows you to compare products before you buy them. If you want a product review I would try Consumer Reports.
Nextel GPS information can be found on the Nextel GPS website. The website will have all the information that one would need. Nextel GPS is a phone software.
GPS City is a website that sells all sorts of GPS units and accessories. The website can be found by typing the store name into your browser and hitting enter.
A Sanyo GPS can be bought from the online retailer Amazon. Also the website allows independent sellers to sell products on their website too. eBay is another site which sell Sanyo GPS.
GPS Pharos are considerably faster than other GPS device's out there. According to this site, it beats another GPS in almost every catagory! http://www.msh-tools.com/magpharos.html
You can read about the Garmin GPS system at the official website. You can also see reviews on Productopia and Consumer Research. GPS Network reviews GPS systems and the GPS magazine has plenty of reviews.
There is no GPS location finder that you can buy, but every GPS will be able to tell you where your location is. Also there are applications that you can download for your GPS that can find locations, and this is usually provided on your GPS manufacture's website,
You can download free software for your gps at download.com. Another good source is to go to the brand's official website. Cnet.com has downloadable software for GPS systems. However, the best place is the manufacturer (TomTom, Magellan, etc) website of your individual GPS unit.
If you are looking to purchase a waterproof gps, a great website to buy these products is at Amazon. This website offers these products at great prices and great quality.
You can go to this website to purchase a quality GPS mount: http://www.bestbuy.com/site/GPS-Accessories/GPS-Mounts-Cradles/abcat0307026.c?id=abcat0307026
If you check out the consumer reports website you can compare any product and get accurate reviews. Checking for the best GPS system and their reviews will be easy on the internet. Another good website is called Consumer Search. You can also search the word GPS and you will get price and review information for all current GPS systems that are on sale.
Lowrance GPS antenna is the most desired brand of GPS antenna. They are reliable, and excellent when compared to other brands, and cost the same as the lower quality brands.
Contact the company that your GPS comes from. You can find their number listed on their website. They will be able to to tell you where to find the necessary items to update your GPS.