Where is the betting window?
I don't know if you are looking at an Altitude 16 or Altitude 32-16 but, now that I've had my 16 for a few months, I recommend the 32-16 (or even 24). Not unlike the rest of this hobby, the "a few more speakers" upgrade bug can be quite addicting. Along those lines, I would wire for a much higher speaker count than 16.
On a more serious note, as I have discovered - at least in my room and my setup, the differences in a well done 7.x.4 room and a 9.x.6 room (or whatever combination you come up with) are not huge. While the additional speakers can help, with such few movies that actually take advantage of them, it is not the big deal I hoped it would be. It is very obvious that while Atmos is an object placement process, the vast majority of mixers are not utilizing it to its fullest. The way it SHOULD work is for an object to be defined by its X, Y, Z coordinates and then have the processor, knowing how many speakers are actually present in the system, make use of the actual speaker count to best place that object in the room.
If, on the other hand, more movies are released that do take advantage of higher speaker counts, then adding even more speakers begins to make more sense. In my case, if I added a 2nd set of side surrounds between my current side surrounds and my rear surrounds, and then another speaker mid-way between my two rear surrounds, I would have a speaker every 30 degrees. But given what I know know from listening to a lot of movies recently (most audio is focused on the front 180 degrees), I would also wire for (depending on width of screen) two more speakers between and L&C and R&C. Also, I would recommend wiring for a total of 8 ceiling speakers.
Two excellent examples of movies that make the higher speaker count well worth it are the new (redone) Matrix and Unbroken.
And as you know, you are more than welcome to come visit again and hear was a 9.x.6 system sound like (where "x" is a fairly large number