The center and front speakers should be matched. From the same line, not just the same manufacturer. You want the same tweeters and the same or similar drivers and crossover.
Also, your center reproduces far more sound than any other speaker in the system, and virtually all of the dialog. It has by far the biggest, most crucial job in the entire setup. Get a good one.
Also consider the Denon X1200W for MultEQ XT over plain MultEQ. Higher resolution on the correction filters.