Adequacy of Mac MC7300?

I need a new amp and have been looking at Magneplanars as well. The Magnepan website says to make sure to use an amp that doubles in power whenever the load impedance is cut in half. In looking at the specs for the Macintosh mc7300 I saw that it was rated 300w for 8, 4 and 2 ohm loads and doesn't appear to put out much current. Does anyone know if this is a weakness of Macintosh amps, or am I missing something? Help!