All Dacs are not created equa and also not all output devices on cd players are created nor are the RCA ins on receivers created equal. Receivers have enough stuff slugging the sound quality that I'd probably use the digital out on the cd player (especially inexpensive cd players) and run the receiver's on board DAC.

Of course exceptions are abound so experimentation is always recommended. A cd player is to be considered a pre pre amp. The cd player has a preamp that sends a signal to a preamp, integrated or receiver. CD players may sound very much the same even if they use different dacs because they use cheap output stages. Thus I can see that using the digital output could improve a number of inexpensive systesm -- I have a $50.00 Aspire DVD player and using the digital out to My Marantz was much much improved. On a good cd player that would be quesitonable.