It would depend on your preamp. A lot of high end preamps have a home theater pass through. Where the signal receives no attention form the preamp. And the home theater processor would still control the volume. They do this so you can have your 2 channel system be part of the home theater. Such as the amp you use in the 2 channel system and your front speakers form the 2 channel system. With out a passthrough i think you would have the 2 gain stages(preamp volume and processor volume) working against each other.
enjoy
enjoy

