Thanks Matt. Some further research has revealed that there are really two lines. The first is Marantz based and uses Audyssey. This would be the 119,121,122.
The second would be Lyngdorf based and used Room Perfect. This would be 150, 151, 160, 170, and now 180.
Based on model year they seem to have similar codex processing, with the most recent ones having Atmos