I am still puzzled about this main-in's on the 520 that ia not available on the 525? My understanding is that the main in's will allow you to use the receiver as an amplifier only, I assume if you down the line wanted to use a separate preamp or processor? Is that right? But, if a receiver has 5.1 or 6.1 inputs, isn't that the same thing, so wouldn't the 525 be able to do that with it's 6.1 input? Isn't playing DVD-Audio through a DVD-Audio DVD player through 5.1 inputs achieving that, bypassing any processor on the receiver and going straight to the amp and speakers? Please leaborate for this newbie?