In the two-chassis designed Duo, there is the obvious elimination of crosstalk, as it's so much easier to design a mono circuit than one for stereo. Everything is simpler. There is more room to optimize the layout, which ends up improving reliability. Both channels here see identical electrical and mechanical environments, so there are less compromises in performance. Sometimes it actually costs more to optimize the performance of a single-chassis unit than it does to build another chassis and go with a mono circuit design.