Try disabling the CC in your receiver. This will send the center channel content to the LR's and provide a "phantom" center image, much like the one presented when you listen in 2-channel mode. If that works, you can get rid of your CC and enjoy, or you can then decide if it's worthwhile to continue to pursue an improved CC speaker.
If phantom CC is not to your liking, try turning off Audyssey. Your receiver has Audyssey 2EQ. If you've run it, it should have set the Speaker Levels and Distances properly. However, 2EQ is the lowest level of Audyssey EQ, and it can sometimes do some wonky things to the signal. (Audyssey 2EQ uses the fewest EQ filter taps, and it spreads them over the entire speaker range, which is not always the most optimal allocation of EQ bands. Higher levels of Audyssey use many more filter taps, and in XT32, concentrates the filter taps at the lower frequency ranges, where they are needed the most.) Try turning off Audyssey 2EQ. (Go into Speaker Setup, -> Equalizer Settings -> Select Off.) The receiver will retain the correct Levels and Distances, it just won't apply the Audyssey EQ. That *may* improve the CC sound.
Ensure the CC Crossover Frequency is 80 Hz or greater. Try 100 Hz or 120 Hz. You might experience some localization of low frequencies to the subwoofer, but that may be preferable to compromised dialogue intelligibility.
Also, ensure that your sources are sending the receiver multi-channel content. In your BluRay player, make sure the output is set to Bitstream. Some BDP's send content as PCM, and that may come across as 2-channel. The receiver would then apply PLIIx to extract the multi-channel signals. This will never be as good as discrete, DD, Dolby TrueHD, or DTS, DTSMA multi-channel signals. Similarly, in your CATV box or Streaming box, be sure your set to output DD content and not just Stereo.
Lombardi said it:
"Perfection is not attainable, but if we chase perfection we can catch excellence.
My System (Edited Feb. 2020 to add 4K and Atmos updates)