How do you know when a stereo sounds good?

when i lose track of time.

The other question I have is why do you sit down one day

and absolutely love the way your system sounds yet the

next day conclude it is nothing special?

The first day you were listening to Kylie Minogue.  The next day you listened to Adele.

You know when a stereo sounds good when the instruments start sounding like instruments. When a guitar sounds like strings vibrating and wood resonating, and so on and so forth. When you walk by a closed door of a room where the system is playing and you're not sure right away whether it's someone inside playing live or a recording.

When I press PLAY and sound comes out of the speakers!

Difficult one...

First when everything sounds better than before.  Totally absorbing and one doesn't want it to be interrupted by anything.  Musicians are in the room.  

Second thoughts....doubt creeps in, is it really doing what I paid all that money for.   What about all those reviews.  Wish I could hear the reviewers system to know if its all BS. Is it my ears?

Comparisons with friends systems help, but in the end I think it could be only experienced reviewers who are able to listen to many systems in their own room that could reach a state of objectivity here.

Ted, would be very interested to hear your views.