A:Answer You can compare tech specs at the following web locations:
https://support.vizio.com/s/article/SB2920-C6-Model-Information?language=en_US
https://support.vizio.com/s/article/SB2920-D6-Model-Information?language=en_US
The primary difference I see, apart from a minor difference in the low freq response (70 vs 75 Hz), is that the D6 supports Dolby Digital sound and the C6 did not. Also, the speaker size shown for the D6 is 1/4" larger than the speaker size in the C6.
I know it's probably too late to help the original poster, but perhaps others have the same question, as I did.
