The Phillips DVD player that I have, had a mention of cleaning up the lenses using a cleaner Disc in the manual.
I tried this after around a year of use using again a philiips DVD cleaner CD. And depending upon your player use, it will make a difference in the sound.
The only other tweak I tried out was damping the player body with M-Seal on the inside (basically you have to add mass to the body and this added mass should have the capacity to absorb the vibrations of the body it is attached to. The best material for this are semisolids). I cannot vouch for the improvement but the sound seemed to smoothen a bit, less grain if you will.
A good tweak will be to upgrade the power supply. The effects can be verfied If you guys have inverter back up for the apartment. Try out by switching off the mains and driving your setup (amps and player) on inverter backup.