I know for a fact that the Vytec does up to 3 mixes but only *one* AI source. I'm pretty sure the D9 works the same way.
Edit: Yes the D9 only works with one transmitter, same as the Vytecs.
IMO, the AI that I had on my Cobra was overrated. For example, the only thing that is actually downloaded to SDM is the starting and ending pressures. This is nothing more than you could easily key in yourself without the AI, I do this with my Vytec to double check my SAC calculations. If you thought you would be able to get your gas usage information throughout the dive you'd be sadly mistaken. The estimated gas minutes remaining is nice for a few dives but isn't accurate unless you dive very square profiles and I soon found it to be more annoying than anything else.
As always, YMMV.