I had the same concerns. I wanted the supercharged SongTowers and, considering how important the center channel is when watching movies, thought if it's good to upgrade the towers it's good to upgrade the center as well. However, I think Jim said mine would be the first supercharged SongCenter ever built so it can't be that big of a concern for other owners.
Would they "match"? Since they have different drivers technically the answer is no. However, considering they each have their own discreet channel I'm not sure how much of a difference it would make or if you'd notice it. Theoretically the center channel would sound better.