If you're an audiophile or in the least bit picky, you're asking a question that you should not be asking. If you don't match the center speaker with your mains, you're going to run into the very good chance of a bad situation.
Think about a vehicle panning from the left through the center and on to the right. If that doesn't make you realize the potential of the problem, it doesn't matter what speaker you use. In fact, you can just use your TV speakers.