From what I've seen of the specs, the MC20 has no issue driving a 4-ohm load for 300-350 watts of power. The Focus 20/20's and Focus HD's are a nominal 4-ohm load so this would appear to be a good match. The only caveat I can offer is that I've never heard the Focus 20/20's driven by Class D amplification (the MC20's are Class D) however the power and other specs would indicate it is a technical match.
http://www.10audio.com/halcro_mc20.htm
http://www.10audio.com/halcro_mc20.htm