How do you know a loudspeaker is the best?

when you find yourself smiling ear to ear unable to utter anything that makes sense and have to be dragged out of the listening room,,,

You don't... and you keep on searching!

1. Go to music store and play some instrument(a couple of notes or so)
2. Go back home play the same instrument through your system.
3. Repeat steps 1 and 2 many times for different possible instruments until the instruments in music store sound near-same in your rig where you have YOUR best speakers.

gunbei said it best.

i recently fell in love with a pair of mcintosh xrt 28 speakers during an audition & was seriously thinking about buying them until i came back home & gave a serious listen to my xrt 22's.

the longer i have the 22's the more i love every thing about them.

gunbei is 100% on target,when you find them you'll know & you'll know in a big way.

mike.

Marakanetz, as a musician, the instrument always sounds much different when you playing it as a musician than when you are listening to it as an audience member. The vantage point is greatly different and some of the sound is likely being inducted through your body and bones.

It's sort of the like the descrepency you notice between yourself speaking and a recording of yourself speaking - although that is an extreme example.