yes, St. Gregory the Illuminator was the founder of Christianity
in Armenia, so St. Gregory is a very common name for Armenian
Churches. I have a lot of friends who are Armenian Catholics who
live near me in the USA.
You are right in that there is an Armenian Orthodox Church, but
there is also an Armenian Rite of the Catholic Church
(http://en.wikipedia.org/wiki/Armenian_Catholic) They have Mass
like the Armenian Orthodox, but they hold Catholic doctrines.