I think it's interesting that both cases were with Avia.

In the sub test section of Avia, there are sub level tests that toggle the signal between the left speaker and sub, center and sub, etc. With 3 different pre/pros and 3 different DVD players, I never had the center to sub test work right (the sub level from the DVD is too low). I wonder if there's other tests in there that might not work 100% correctly...