I recommend giving the previous suggestions a try. When I upgraded to my current configuration, I still didn't care for the sound coming out the center even after using the auto balancing feature and mic on my receiver. So I manually upped the center channel a bit and I am happier as I can hear the dialogue.
Now, I occasionally have a problem where I can't hear my center channel. But I have learned that I may have been an idiot and left it in 2-channel mode.
I have not used an SPL meter. But some movies don't have the center audio as well balanced as I would like. Take the new Sherlock Holmes movie. It's center sound is not as bright as I would like for dialogue purposes and the base is really loud (on my system). So sometime you may have to fudge your system for specific movies. Just my opinion.