The clocking of a digital player has nothing to do with the display. If you unplug the clock, the player will power up but you will not be able to play CD. In recent more sophisticated players, if the clock is removed, it will not even power up.
In the case of the display with all CD, SACD and Universal players, when it is shut down, the sonics are much better because the Display driver IC clock interferes with the audio clocks and data. Many players have Display OFF function. Some shut the clock and put the processor to sleep which brings best results, some dont.
If you completely disable the display by pulling off the plug from the main PCB, you will gain better sound, but will totally loose control over the machine (manual or remote). So, you can do this only to experiment while it is already playing, but before you plug it back, make sure the machine is OFF. Not that you will burn everything the first time, but it will happen soon or later. :-)
Regards,
Alex