To be honest, these aren`t much cheaper than the CS60. the 60 is 8-note poly instead of 4, has 5-octaves rather than 4, has the wonderful Ribbon controller and one slider panel "memory" both missing from the 50. this negates the little 50 totally unless either the 50 is very cheap or you just can`t get a 60. Dead CS50s however are a CS80 owner`s best friend.. they all sound the same, IE Wonderful a good slice of CS80 in a reliable comparitively light package. BTW it`s the 60 that weighs 46Kg, the 50 weighs less.
(It`s only getting a 3 cos of the 4-octave keyboard, I HATE 4-octave Kbds on polysynths), as a source of spares a dead one would get a 4 (;-) a dead 60 would get a 5.