Sorry that I am late to this party! Back when I was first able to audition the IP322, and Jim was telling me about the capabilities of his on-board DSP, one of my first comments was, 'Hey, now you can do bi-amping
right!'

And, that blossomed into the discussion of time alignment, phase coherence correction, etc. to make a 3-way cab work as well as possible. Well, Jim likes to tinker, and he tinkered with these ideas for some time, and I gotta say, it's worth the effort!
As I told chadds when he asked me what the IP153 offered relative to the other (excellent in their own right) IP cabs, the phrase that came to mind is that while all the IP cabs are very balanced and even in their response, very loud, very dynamic, very full, etc., the thing that really pops about the IP153 is that 'effortlessly articulate' thing. It is one of the 'fastest'

cabs I have played. Just amazing. For those who heard it at my GTG, it has been through at least two DSP programming changes since then, and is now really fine tuned and kicking even more A.
Not sure if all of these questions were answered, but no, the 15" is not neo, and yes, the 6" midranges are the same as used in the NV215.
The low end is sufficiently different from the IP310, btw, that anyone who struggled getting controlled low end in some rooms will probably have better luck with the IP153 than with the IP310. The IP310 has that '10" roundness' to the deep lows, and the 15 is more attacking and cutting.
I may have to get three of the IP153/EX115 stacks. One for my bass rig, and one for the 'new and improved' Berg PA.

That way, I can leave that rack full of CA9's at home!
Tom.