@eric_squires ..."Well, I think the improvement has more to do with a mediocre center channel."
+1
I agree. There was something wrong with the center channel. Perhaps the center had been malfunctioning all the time, and finally went out.
Most of the sound on HT comes through the center channel. It is primarily responsible for dialog. That is where the clarity comes from. When I use my home theater without the center channel the dialog looses weight (big time) and clarity.
I recommend looking at this as if you have had a center channel problem long before the center died.