Interesting topic!
Some of the Beatles Love album has some nice wide effects. It is best to have a speaker that accurately represents the stereo image to really hear EXTREME width.
In the studio, there are lots of tricks to widening the stereo track. It is usually done with MS (mid side) processing. Essentially what happens is you increase the differences between L and R- that is the content that is thrown outside the range of the speakers.
You could play around with widener plugins on your music library to see how wide you can make it.