No you don't. The GPS Receiver capabilities are pretty much the same on the inexpensive units as they are on the more expensive units. The money comes in to play when you start adding features like Base Maps, Cartography, Auto-routing, etc.
Garmin is one of the more popular manufacturers but they are also one of the top leaders in advanced GPS Technology. Garmin is nearly a stand-alone name in the aviation community where we use both their handhelds as well as the panel mount units. A lot of the technology comes from the aviation industry.
You can buy a Garmin eTrex at Wal Mart for about $100 + or - and it would be totally capable for use in Geocaching.
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