I wrote to Mazda recently in regards to the HID option on the 2004 models and I have cut and paste their response to my email below. Feel free to contact them and verify this if you wish in regards to nav because I do not know about that.
Thank you for contacting Mazda North American Operations. I appreciate
the opportunity to respond to you.
At this time Mazda does not have any plans to make the HID headlights
available for the 2004 model MAZDA6.
I am pleased you took the time to bring your suggestion regarding HID
headlights to our attention. Consumer feedback is always very important
to Mazda. Certainly, we want to offer exciting vehicles, and comments
such as yours help us to achieve that goal.
Rest assured I have documented your suggestion for our corporate
record. These records are continuously being reviewed by our Product
Planning Department in an effort to provide only the highest quality
products to our customers.
Again, thank you for contacting Mazda. It has been my pleasure to
assist you. If for any reason this response has not completely
satisfied you, please feel free to reply to this message. You may also
contact our Customer Assistance Center toll-free at 1-800-222-5500.
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Specialist, Customer Assistance E-Business