For all those NC owners out there that thought they were stuck with the factory stereo headunits there is still hope. I came across the following installation while in Seattle Washington, USA for the Northwest Miata Club's Backroads to Bavaria weekend, as organised by John Hewitt.

It is hard to tell due the angle of the photo, but that is a Pioneer fully intergrated navigation/sound system. The owner told us that it took around 2 hours to install. More details will provided once the owner provides them to us.
J