Surround back speaker. Same as front center?

As I understand it, the center speaker is important to focus/image the speech or dialogue audio in the movie to match the location in the image viewed. It is important for this to blend properly with the left and right channel speakers so should be "voiced" accordingly (probably should be same manufacturer and with usage for that purpose). The rear/side channels provide "ambient" sounds and should not be so noticeable as to draw attention to themselves when properly set up. Hope this is helpful.