I'll echo what others have said and say that I certainly wouldn't worry about the factory NAV. Any modern aftermarket NAV is going to be vastly superior to the antiquated (in electronics terms) BMW system. The only downside (to some) is dashboard aesthetics. Personally, even though the factory system certainly does look "factory", I think it also looks (and definitely functions) as "old".

I wouldn't pass up a good car just because it did or did not have NAV. Most NAV systems (maybe all?) are also DSP systems, which does complicate an aftermarket head unit install. If it does have DSP, then you'll have to buy an aftermarket five-channel amp (and some crossovers) to get the new head unit's sound to the factory speakers. A little added expense to keep in mind.

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