Hey guys, I don't have a nav unit on my x5 nor do I intend to replace the stock unit. Anywho, any model suggestions on a good portable navigation unit (magellan, garmin etc)? Budget is $500-800. Any feedback on those who know about or have used a portable navigation unit before would be greatly appreciated. The simpler and the more user friendly the better. Well, the more bang for the buck the better. Thanks.