I have been a GPS user for many years as a sailor. I am planning a bike trip to Europe in March to stay over there for probably 6 months. In getting the bike ready in addition to panniers and other stuff I purchased a Garmin 450 handheld to mount on the handlebars. I did not purchase the t unit to avoid the premium of topo maps. I have just loaded various US topo maps on the unit from this website. I am very impressed with the Alabama topo that is available here. I am also going to load what European topos that are here as I wander Europe this summer. This is simply a thanks for the excellent maps. Searching now for European (and US ) cycle trail maps.
expat42451
Be sure to check this site: http://garmin.na1400.info/routable.php
It uses OpenStreetMaps data which is an international project to provided free road/street/trail data. The user input is extensive and very detailed for much of Europe.