Do you have a sub and what is crossover settings? Does your center sound muffled all the time, and under what conditions(music,dvd,cd,cable...)? I'm not very familar with the denon avr 1603 others may help. Are you using any type of DSP or are you using Dolby Digital or DTS?. Is your...
I would consider the 37c an excellent center speaker. Check all the drivers in the speaker and make sure they all are working. The tweeter is acually known to fall out during shipping. What other pieces do you have in your system, you may have a setup problem.