A Source Four PAR EA utilizes the brightness and efficiency of the HPL lamp from the Source Four line, but it has an Enhanced Aluminum reflector. The aluminum reflector does not have the cold mirror technology as the MCM line, but it supports lamp wattages up to 750 watts.
A Source Four PAR MCM has the above features, with the same type of Metal Cold Mirror (MCM) that the Source Four Ellipsoidal line has. The MCM line is rated for HPL lamps up to 575 watts.
See also: KnowledgeBase: Source Four Heat Ratings/ How Much Heat Does the Source 4 Emit?