I would call the soundstage "the goal". With that goal, each system will do it differently, each room different... yes it should be musical, engaging, with magical tonality, dynamic(micro and macro), with PRat,... all important too! (as mentioned way more eloquently by blindjim). Each above as definied by the listener.
"the goal" (for me) is when you can walk around the room, say from a couple of feet back from the speaker (so its drivers can become a point source), walk throughout the room, and the "characters" stay locked in their proper locale as you move, they do not! With good hall info or venue acoustic(for me). (assuming the recording has this via production values, manufacturing processes,...)
It is a system result, of having "synergy", as beerdraft states, things "lock in".. First your speakers should dissapear as a sound source, the room hopefully as well; your electronics, source, preamp, amps, have to be able to allow your speakers/room to do it's thing. Then Cables too (alot of cables do not "stage" here, as you move around the room, so does the stage move with some cables here, they may sound OK, and things from the sweet spot may appear OK, but it is not truely all that focused or locked in as made apparent as you move around the room - or even as your head bobs to the music). Each room is different, rules of the room (living room versus dedicated cave), budget (sometimes we cut corners on good cables, isolation; for various reasons stay loyal to a component that may or may not be delivering the goods as well as another could be...), tastes and preferences/priorities of sound. And it is work, listening THAT HARD, to figure out what it is you are listening too, "the set up"; speaker placement, the room, component placement, cable placement, all the various tweaks, Tube rolling, isolation devices, power cords, IC's, tube dampers, cartridge setup/phono stage - everything effects everything else - not just the speaker's ability to stage or the placement of that pair of speakers in that room.
It is real work to get it "right"... but after cleaning your elbows, the sound you are left with, can really tug at your heart - regardless of the mood you step into the space with, you cannot deny the emotions the music before you brings forth. The "snapshot" of that recording at that moment in time, replayed for you... that moment recaptured and replayed at your leasure, in your space,...
