TOPIC:

Other than the obvious number of channels difference, which is not critical to me as I only need 8 outputs, what are the key differences in features? i.s. PEQ bands, filter types etc. I can't find a way to do a feature comparison...

6x8
6 PEQs per channel
Delay limited to ?

8x12
10 PEQs per input and output channel
Delay up to 25ms
Higher S/N Ratio
Higher Stereo separation
Can be configured for true differential rear processing (L-R)
Can be firmware upgraded to Dirac in the future with no additional hardware.

IMHO - I would definitely go with the 8x12 if your budget allows. It's the best value in a high end 12v DSP whereas the 6x8 is a basic, limited function beginner DSP that is not upgradable.

I had great luck with the 6x8 in my previous install (first foray into DSP) but given these differences, I ordered the 8x12 and I'm looking forward to the tuning process. (still have to do the install grunt work lol)
The 10 vs 6 PEQ I think is the biggest value for me. I really struggled to match my target curve properly with just 6. I believe there are also allpass filters available on the 8X12 which I don't remember having on 6x8 but I may have just missed them...