Disklavier

When I play my MPX70 in Silent mode, the basic piano sound is not at all bad, BUT the elderly processor appears unable to keep up with the number of notes being played (along with use of the sustaining pedal) on stride piano solos.  The result is that the sound of the notes can be delayed, with chords in particular being broken rather than sounding in unison.  Examples of the type of music which causes this problem can be found amongst my YouTube videos (my user ID is honkytonkpiano).  I suspect that the MPX70's sound generator simply doesn't have enough computer power, and that the only solution might be to acquire a separate sound generator unit to accept the MIDI out from the MPX70.  I would be grateful for suggestions (other than DON'T PLAY THAT TYPE OF MUSIC ANY MORE!!) 
Thanks in anticipation, 
Mike Thomson