Mirage Omnisat v2 or Nanosat, or the center channel version of either. They're all very small and omnipolar, which means you get wide coverage from a very small speaker. Center channel clarity does NOT suffer, however. Their midrange is exemplary, the synthetic enclosures with non-parallel lines avoid boxy resonances, and the Omnisats are linear down to 70 Hz for an easy and safe handoff to the sub. Power handling of 150-175 watts, too.
Check 'em out here.
Check 'em out here.