Can someone explain to me the value of preamp outputs? What makes them such an important feature of a receiver? As I understand it, these outputs are used when you want to use another amplifier. When would you use another amplifier? I apologize in advance if this is a stupid question. I'm trying to make a final decision in my receiver purchase. Right now I'm considering the Yamaha HTR-5490. I reading this Forum, many people think that this unit not having any any preamp outputs is a real draw back. Can someone explain??