It's good you are shopping for a Navi unit now because the maps have been upgraded recently and any 07 or 08 Garmin unit has the fresh info.
With big cities growing so quickly, you need fresh maps to find your way around the all the new ring roads, and overpasses being built.
We use a Garmin C330 between our Honda Odyssey and the Versa. I built a mount base for the Honda so that it sits in the ash try unit when it's pulled out. In the Versa it simply sits in the driver side cup holder in front of the transmission selector.
This put it down under the dashboard and it had trouble getting a good sattelight fix, so I installed a remote antenna on the dash close to the windshield and that gives it a great view of the sky for signals.
I can't count the times when we would have been lost without it, looking for addresses in Dallas Tx, and Albqurque NM.
If you click on the link below and use the "Slideshow" feature it will auto scroll and enlarge the photos of our Versa Album with the Navi unit.
http://picasaweb.google.com/longo3002/VersaPics