Hands down, having 2 fronts will give you MUCH more enjoyment than a single center.

Think about it - would you rather have mono or stereo sound? Plus, chances are that even if you do have timber matching speakers (for the 3 in front), the stereo L/R speakers might have larger woofers to give you deeper bass. You'll also have a wider sound stage with the 2 speakers(which you can adjust by simply changing the distance between the two).