Are you looking for a removable nav or a built in. If you want a removable one then get a Garmin unit, I suggest the new 2610/2650 models comming out. The portable units can be moved to other cars, taken with you on hikes, and can easily be updated by downloading updates from the internet. Disavantages: not as many features, can only hold a state or county, usually looks ugly or out of place on the dash, and has a small screen. The Garmin 2610 is avalable for pre order on amazon.com for $850 making it the cheepest option, it comes out end of this month.
For built in ones, get the Kenwood or Alpine. I all depends on how mutch you want to spend and what features you want. If you want a built in one, you are looking at around $2000 and up. There are many advangages sutch as having the entire United States on 1 disk, being able to watch DVD movies, more features, mutch bigger screen, and easier to use. Disavantages: requires profesional instalation, expensive, an updated disk can be costly. The Kenwood unit is selling for $1500 + another $1100 for an 8" screen at Crutchfield.com. The Alpine unit is selling for $1700 + $650 for a 6.5" screen at Crtuchfield.com. Also add to that instalation, and tax. Some of these models can be found for cheeper if you search for it, Crutchfield's price is very fair and cheeper then most retail stores.
If you want a built in though, I would suggest waiting, there are many new advancements comming to the built in market including traffic reports. The nav would get updates on accidents and traffic and be able to re route you around them. These features are less then a year away if you want to wait.
If you have any questions feel free to ask. By the way, congrats on the new BMW
![Smile [:)] [:)]](/images/smilies/smile.png)