Fanum is correct - there are many newer products from Garmin that are available for prices similar to what you have quoted, and these newer products would be a much wiser choice.
There are several problems associated with buying a very old piece of equipment such as the SP III. One is the condition of the backlight that illuminates the screen - that particular type of lighting technology tends to degrade over long periods of time (e.g. 5 years or so). The other is the matter of 'how current are the maps?' It's no bargain to buy a GPSR for a low price, then find out that the cartography is 4 or 5 years old, and thus grossly out of date.
Honest - forget about buying a SP III, have a look at what is available as current product - either 'new in box' current product, or 'gently used but still being sold as new elsewhere' current product. MAKE SURE you are aware of the version number (age) of the maps that come with the unit if you are buying a used unit. That is the number one oversight that people make - they buy a used unit, then find out that the maps are way out of date, and have to fork out a whole ton of money to purchase current maps. Total cost of an error like that is always greater than the cost of buying a new unit at a local retailer.
Michael
I don't know if you can do a search (as you're not a sponsor) but if you can, search for "paneuropean" as an User name - that will keep you quiet for hours. 
