Not sure what 8 channels would do for you...
2 Front
1 Centre Front
2 Rear
2 Side
1 Centre Ceiling
+ 1 Sub
--------
8.1
Does anyone even offer DVD/BD with such Encoded?
2 Front
1 Centre Front
2 Rear
2 Side
1 Centre Ceiling
+ 1 Sub
--------
8.1
Does anyone even offer DVD/BD with such Encoded?
Since 9.1 adds 2 high front speakers to a 7.1 setup, 8.1 would likely add 1 high front speaker located in the center. That's how it works with 6.1 using 1 rear surround speaker in place of 2 rear surround speakers for 7.1.