I believe that hopjohn has pretty much hit the nail on the head. However another factor that must be considered is how you are connecting the player to your receiver (analog or digital), and quality of the DACs in your receiver vs the DACs in the player. If your receiver has quality DACs and you are using an optical connection the differences between players become almost negligible, barring that they are of sound design. If you are using the an analog connection, and thus the player's DACs, and the player's analog output stages the player becomes much more of a factor, and thus there may be an improvements in audio playback. As always the law of diminishing ROI is in effect.
Simple right?
PS I love my universal’s Redbook playback!