But considering the resolution and size of the factory screens, I'd question the difference in quality vs standard definition. If the screens can't pump out high(er) resolutions, then it wont matter what you throw at it.
if you have a newer HDTV or EDTV with a Digital tuner built in, don't worry about the switch. if you have a cable box or satelite box, again don't worry about the change because the boxes are ready for it. the only people affected are those that have an older "tube" tv and are using basic cable pluged into the back of the tv, or an antenna on top the roof. i manage a home theater store and this is one of my most common questions. if anybody needs help with anything HD or Surround Sound let me know.