Montepilot,
If I could jump in on your question to Rushton, re: "a good tool for capturing voices as they move about the stage" I have found Holst's "Savitri, A Chamber Opera In One Act" perfect for judging soundstaging and where both male and female performers are on the stage, as they move upstage to downstage, right to left. It is on the Argo label (ZN 6 if I'm not mistaken).
I am sure Rushton will offer some fine suggestions of his own, but he and I both agree on the "Savitri"