I'm with Bruce in concept, match those front 3 speakers. But I have to disagree about the golden ear comment. Noticing a difference in the timbre of front/center speakers is very obvious if you try. It's not like comparing 2 sets of speakers for which is better. You just have to set them up properly and then see if you can hear each speaker. If you can locate the center, it is either a different speaker or not set up properly.

That's why I think it is so important to have matched speakers. I've tried it the other way and it is not nearly as immersive.