Close enough.

In the second I am steadfast and stout (Steadfast and stout have the same meaning as stalwart)
In the first I am called by another (Barbatos and Vorban look just like Stalwart)
In a place of damnation you'll find me (Damnation = sin. Barbatos is Inside Sin)
And in a place of aquisition I reside. (Vorban is in the Monster Arena, which is the place where all the fiends you have acquired are stored)