What you're experiencing is the difference in volume of the voices on the track and the explosions (which are louder) due to the dynamic range of the audio track. Basically, the dynamic range is the range of volume (from the quietest moment to the loudest moment) played in the track. The mix has been intentionally done this way so that the explosions have the impact that the director/sound mixer intended.
In a theater it usually is not a problem because the volume is turned up loud enough to hear the voices. The loud explosions are relatively louder too, but this isn't an issue in a sound-isolated theater - without babies, roommates and neighbors to worry about.
One thing you can do is limit the dynamic range on your reciever (by making it narrow, rather than wide or normal). The narrower the dynamic range, the less difference there will be in volume between the quietest and the loudest sound. There may be some changes to the quality of the sound - what they may be, I am not sure. The limited dynamic range will ensure that the voices will be loud, but the explosions don't have the neighbors banging on your door.
About the whining of the high pitched voices - that might be caused by the amp straining to produce a lower level signal at a higher volume (guessing here). In any event, you may find the problem solves itself by narrowing the dynamics. But understand that it might come with some negative side-effects with which others may have more experience which they choose to comment on.
hope this helps.
