Come vote for every Reformer's favorite early Christian,* Augustine!
*I'm only mostly joking.
I pulled up the Concordance tool on my Battles translation of Calvin's Institutes....
573 links to the works of Augustine. The Verbum Augustine collection would include a more readable The City of God, The Trinity as well as many of the Anti-Pelagian works Calvin references. In addition, the collection includes two volumes of Augustine's works on the Psalms, which are cited by Calvin often.
99 links to the works of Cyprian, and the Verbum collection would include newer translations of just about all of these works.
52 links to Gregory the Great - although there isn't much overlap
30 links to Jerome - again not much overlap
25 links to Irenaeus - and 18 of them would be to a fine late 20th century edition that is aware of actual Gnostic writings.
It seems to me that if you are serious about Calvin, you should have some awareness of those with whom he interacted. These offerings let you experience many of these historical Christians on their own terms.
[Y]
St. Augustine is in serious danger of winning it all... or losing.