1. If you have a dish like DirecTV, you need to buy a HDTV decoder for DirecTV. You also need a HDTV cable box but it is usually supplied by the cable company.
2. You don't need a HDTV to view 480P (progressive scan DVD player). You need a TV with component inputs and have wide enough video frequency response to handle the 480P signal. Nowaday, all the mid-price TVs with component inputs can do that.
If you want to do 720P than yes, you do need a HDTV set.
3. I like component input because it is the more compatible form of connection. Some HDTVs also have DVI and RGB inputs. DVI is for HDTV signal and is supposed to be the best but they might suffer compatibility problem across brands. Also on most TVs DVI input is fixed on a particular resoultion. RGB should be better than component also but RGB cables are more expensive. Unless you have a front projector, you won't see much different on most sets.
2. You don't need a HDTV to view 480P (progressive scan DVD player). You need a TV with component inputs and have wide enough video frequency response to handle the 480P signal. Nowaday, all the mid-price TVs with component inputs can do that.
If you want to do 720P than yes, you do need a HDTV set.
3. I like component input because it is the more compatible form of connection. Some HDTVs also have DVI and RGB inputs. DVI is for HDTV signal and is supposed to be the best but they might suffer compatibility problem across brands. Also on most TVs DVI input is fixed on a particular resoultion. RGB should be better than component also but RGB cables are more expensive. Unless you have a front projector, you won't see much different on most sets.