Look on eBAy, that's where I got my eMap and now that the Gekko's are out you might find a good deal on a used eTrex; BE CAREFUL ON EBAY, check a sellers feedback carefully and even then you could get a bad deal but not likely.
Just remember that the more the GPS unit does the faster it eats batteries and $$$. Also Garmin accessories are quite pricey and can be had for half the price from third parties on eBay.
I'm biased toward Garmin because it was my first GPS and Garmin was the first out with a small unit.
I started with a Garmin eTrex then got an eMap for the mapping capability. Still when I go backpacking I take the eTrex because of its' size and battery life span plus the eTrex is water resistant (Garmin says waterproof) where the eMap is not. The eTrex also has more navigational information than the eMap..
The new Garmin Gekko is virtually the same as the eTrex but uses AAA batteries instead of AA which means even less ON time. Also the smallest Gekko has no PC interface capability. Having a PC interface is real nice to get the cache points to your GPS and to keep a log of them.
Oh, and a compass might be nice too so you know the direction you're facing; unless you're moving a GPS does not know which way it is pointing unless you have one of those fancy units with a compass function.