I think that it is a mistake to limit the cast voices to named characters. There were many, many unnamed and incidental characters. John DiMaggio, for example, was the Booth guy in "Emotion Sickness". He was also Heinrich, Akut and Captain Louis. Those are just examples.
The end credits for season 1 are different in the International and the US broadcast versions. / The International credits listed the overseas animators. The US broadcast version did not. / In most (but, not all) episodes, the US version credits J. Lampinen for 'Digital Audio Transfer'. The International one did not. / Anna Boyadjian's credit is 'Production Accountant' in the International one. It was 'Production Control' in the US version. / The International credits had white non-scrolling text on a blue background. The US broadcast version had white scrolling text on a black background. / And, finally, the five season 1 episodes reedited with songs (US only) had the song credits added.