This is how I imagine some characters.
Jesse L. Martin seems to be the most popular choice for Sam Bowers.
Taran'atar: Christopher Judge
Shawn Christian looks perfect for the role of Calhoun, and he's a good actor.
Rosalinda Celentano certainly has the face for Burgoyne 172.
Soleta: Jennifer Morrison
Si Cwan: Arnold Vosloo
Christine Vale: Katee Sackhoff
Xin Ra-Havreii: Jeffrey Combs