It will only degrade the sound, even though it's a very good cap. On the headphone out it's not needed as there are already some caps there to block DC.
The sound is about spot-on as oimp caps are smoother, warmer sounding and slower. If you like this, then no harm is done by adding this.
But if you mod the cp player thaking out the original caps and direct connect to the vcap then you would have the best as you would improve clarity while sounding warmer.
siang