I'm in the middle of trying to decide which preamp will center my rebuilt home theater. What is really nagging at me however is this whole analog input situation with DVD-A and SACD. Some receivers have 7.1 channel input, others have 5.1. Does that mean that a 5.1 input system cannot use the other two speakers in a 7.1 speaker set up? How should one hookup a 7.1 connection for DVD-A and SACD? Just double up on the back channels? Thanks in advance for any help!