One of the hallmarks of a great high-end audio system is a convincing image.
How real does the soundstage come across? Is it believable or contrived?
To know for sure, it's important to have a reliable source of properly recorded music. After all, if your recording isn't up to par no amount of setup or tweaking is going to deliver a convincing image.
One of Octave Record's recent releases, Conversations, has exactly what we want. A truly convincing soundstage (plus great music!).
How did we achieve this in the recording? Simple miking techniques. Instead of the usual multi-mic arrangement, we instead placed the musicians around a single stereo microphone and then added only one spot microphone on the cello (because it is so much farther away from the microphone than the violins and viola).
Another recent Octave release, Audiophile Masters VIII, also has a couple of outstanding tracks that present a truly realistic and convincing stage. Try Track 7, Four Pieces for String Quartet Op. 81 MWV R 35, and get the level just right. Then, close your eyes and tell me if those musicians aren't in the room with you.
Having the right reference material to help with setup or simply to enjoy the work you've invested in is a must for any good system.