Navigator/dvd Player

Im thinking of upgrading the standard stereo in my Camry to a GPS/Navigator.

Does anybody know if those Navigator units can also play DVDs? Also, equally as important is will i still be able to use the steering wheel mounted controls on an aftermarket unit?

With these in mind, does anybody have any recommendations of Brand and/or model that would suit my needs? I always used to buy Alpine when i was a boy racer, but these days they seem to be lagging behind somewhat unless you are a real soundman.