Upon looking for some 8" options for a DIY design and posting these as a possibility, I was informed Revel is likely using the drivers (with some tweaks, obviously) in their F208.
So, I ordered up a set and just wrapped up some small and large signal testing of the SB23NACS45-8.
Mfg site:
SB Acoustics :: 8" SB23NACS45-8
My data here:
http://medleysmusings.com/sb23nacs45-8/
The data isn't quite what I was hoping for *for my intended application*. I was hoping for some more linearity here, to eek some more output. That said, without the offsets, you might get 1mm more in linear excursion and if the suspension was more symmetrical, it would give you possibly 0.5mm more. So, there's not a huge gain there.
Looking at the FR posted by SB on their site, combined with my measured T/S and the fact there is a shorting ring used here (which will help knock down higher frequency intermodulated distortion) it looks to me this was designed more with 2-way use in mind rather than solely as a dedicated midbass. Using (2) of these, like the F208 does certainly helps in terms of output.