Interesting that Paul McGowen's post today is on this subject. Here's his para-phrased opinion of it:
"SoundStage: It's already in the recording!
…A stereo recording carries spatial information as tiny amplitude and timing differences between the left and right channels. That's it. Our brains are extraordinary at decoding those differences into a coherent three-dimensional picture — but only if the playback chain preserves them faithfully. Move a transient by a few microseconds, smear it ever so slightly, and the picture starts to collapse inward. Center images thicken. Instruments drift forward. The speakers stop disappearing and start politely reminding you they're sitting in the room…Most of us have had the moment where we swap one piece in the chain and suddenly hear the room behind the singer for the first time. That information didn't appear from nowhere. It was always on the disc, in the file, on the master tape. Many of us have spent thousands chasing what the playback chain was maddingly deleting all along…The chain matters from file all the way to ears, every link of it. Strengthen any one link and the whole picture gets a little more believable…Soundstage isn't something a piece of gear gives you. It's something a piece of gear stops taking from you…it’s the absence of every little smear and timing slip that quietly flattens a recording."