The Garmin 1400 series fits the cubby hole, this is my fit wired in to ignition for auto power on and off.

Garmin Nüvi is cheap and cheerful and fits reasonably well. Mine is a pretty basic fix but does the job, see http://www.freel2.com/forum/topic8949.html?highlight=satnav for info and there is a link to some pics in my gallery. Sound is integral to the unit, and it does work when mounted in the dash hole.