Playback and Dynamics Balance on MS4

I can't get what is so stressing about using the new playback sounds system... I can barely hear the clarinet, and voices are almost non-existent in between orchestra. On the other hand, piano and solo strings are incredibly volumous. I know I can master the sounds with the very accessible Mixer, but it is no small effect: The choir is always on maximum until I can hear it! Dynamics seem to have little effect, although cresc. and dim. lines are now responding better. Also, why isn't there something as simple as an X to quit the Mixer??