Any of the WAAS enabled GPS units will be much more accurate than the older ones without it. I would recommend the Garmin Map 76. It has a larger screen than the Geko and Etrex series, which I've had both of and they are just as accurate but the screens are small. You can get a new Map 76 off the Internet for under $200. Discount GPS has lowered their price again - http://www.cartserver.com/sc/cart.cgi. Be sure and click on "Click for Your Price" - $170 including a data cable and shipping.
You need the data cable so you can back-up your waypoints on your computer and you'll want a power cord/adapter because they do like to eat batteries. You can get cables at very reasonable prices from - http://stores.ebay.com/RNRPLACE_W0QQsspagenameZl2QQtZkm