I'm connected to a 42" Plasma TV that is (only) an EDTV. [...] I have only 852 horizontal lines. But it can take signals up to 1080i, regular DVD is 480p, upconverting is 720p which is what I wanted.
Actually, one of the best advice about setting up a new Plasma or LCD tv is to spend the 300$ or so to have it professionally calibrated. If you can't afford it or don't have access to that kind of service your should at least spend the 30$ to buy a calibration DVD.