City Navigator is a must. There are European versions out there. Try eBay and other online retailers because you can find it for well under $100 U.S.
I have TOPO US 2008 and City Navigator North America and it works great. I loaded all of the continental US City Navigator Maps and California, Oregon, Nevada, & Arizona Topo Maps on an 8GB Micro SD card ($12.00 U.S.). My maps take up a little less than 3 GB on the Micro SD card. I would have loaded more, but it takes to long for mapsource to compile the maps.
So, that leaves a lot of room on the card for other stuff. Be aware that the Oregon has a limit of 4GB of map data. The Oregon also has a limit of 200 GPX files and a 2000 geocache limit. Be aware that GSAK (available at GSAK.net) can load 2000 geocaches into one gpx file which makes the GPX file limit of 200 a mute point. Oh, make sure that you do not use your Oregon without a screen protector. You don't want to get a nasty scratch on it before you get to enjoy it.
There are free maps out there like IBYCUS. I'm not sure if they cover Europe, but here in the states it gives you pretty good detail without auto-routing.
By the way, you are going to love the Geocaching software that is built in.
I hope this helps.
JeepDelFuego
Yes it helpt a lot, thank you very much