Personally, I think compression is the last thing you should try. It may be the easy way, but it's not the right way. The more dynamic the better!
First step is to calibrate the volume of the speakers in the system. A test disc and SPL meter are required for this if the receiver does not auto calibrate.
Next, the distance needs to be calibrated.
Speaker placement is very important. If the speaker is on a shelf or on top of the TV, you can get a lot of diffraction which can cause the voices to sound muddy. If the speaker is on a shelf, pull it forward until it hangs in front of the shelf slightly. Another culprit can sometimes be the coffee table directly in front of the center channel.
If all these things are addressed and there's still a problem, you may need to treat first reflection points of the L/C/R speakers with sound absorption. By reducing the reflections, your ears and brain have fewer sound waves arriving at different times and it makes it a lot easier to understand dialog.
If all else fails, get a hearing test.