John,
Check the plugins page: (2x8/8x8 plug-ins tab)
http://www.minidsp.com/products/pluginsIt's my understanding the 4x10 plugin will work on the 8x8 board and yield the 96khz operation (for two inputs only.) If utilizing the 10x10 plugin then the sample rate capability is reduced to 48khz.
I believe the only difference between the two boards is population of hardware to support the extra inputs. If a user doesn't envision a possible usage of more inputs than provided by the 2x8 board then the extra cost for the 8x8 board should not be necessary.
For some folks there might be no point, but for others maybe that extra versatility might be a useful feature.

Anyways, I don't think the statement that "miniDSP 8x8 card does not run at 96khz" is accurate.
Cheers,
Dave.