Please do not get a folding monitor. They end up breaking more often and are generally of lesser quality. You can easily fit a double DIN head unit in there and it will look almost entirely stock. If you have the manual climate controls (IE there is no digital display on them) you can pick up a dash kit for roughly $30 that will look completely stock. I've got the auto climate controls, but it still looks fairly stock (to the untrained viewer):
With the manual climate controls, you can do this (not sure who's pic this is, I stole it from a GIS - sorry):
As far as the speakers go, just tweeters and nothing else? May I ask why?