I saw the Northstar 538i when I was looking and it seems like a sweet deal for a discontinued product.
http://www.hayestrading.com/storefro...d=10165&dfid=1
Best part is the unit has built in fuel monitoring software, you just need to add the probe for a couple bucks and you are done. Don't know too much about navman/northstar but everyone that has them seems to like their gear.
-Svence