Tower is indicating that the 6EXA is discontinued, and has been replaced with a 6EXAS. The only difference I can see right off-hand is that the 6EXAS contains 4-character model naming, while the 6EXA only had model #'s for different models. There's probably more programming enhancments that haven't been identified yet, since the 6EXAS isn't due out until the end of April.