Preamp inverts phase question:

Yep.

You may or may not hear a difference.

My Calypso has a phase inverting feature which can be switched with the remote. Is this similar to your preamp. If it is the purpose is to be able to shift phase because some music is recorded out of phase (by accident ?) and sounds better played back out of phase. Most of the time when I shift phase to check it doesn't make a difference.

The purpose of phase in a speaker is to make sure that all the speaker's all push out and pull back together. when speakers are out of phase, one speaker is pushing air into the room when the other is pushing away from the room...and that cancels out the sound. It's like two sine waves where one speaker is all the way plus while the other speaker is all the way minus.

For hifi systems (stereo or Home theater), as long as all the speakers are wired the same way, it doesn't matter .... all of the speakers will be in the same phase. It doesn't matter which is plus and which is minus as long as all the speakers are wired that way.