One MC100 for Right Channel and one MC100 for Left Channel. The ultimate in vintage McIntosh SS mono-blocks! Of course, finding a 2nd will prove to be a challenge.
OR, as c_dk suggested, pair the single MC100 with a MC2100 and a Mc preamp of the same vintage with a Center channel output to create a 3-channel audio system, popular in the '70s. This was common for folks with Klipshorns. Khorns have to be so far apart to image correctly when your seated 10 feet from them so a Belle, LaScala, Cornwall, or Heresy was commonly used as a center channel speaker to bridge the gap so to speak. The system would have looked something like this:
C26 or C28 preamp
L&R Outputs > MC2100 (or MC2105) > Klipschorns
Center Output > MC100 > Belle