That's probably a good test for your space.

No DVD's are encoded in discrete 7.1 - no such format exists outside of HD-DVD and Blu-ray. Dolby EX, DTS ES, and even DTS's NEO:6 matrix decoder are technically 6.1 formats. Pro Logic IIx can produce discrete left and right surround back channels from 5.1 sources (the 1070 can do it with Dolby or DTS, although not all receivers can with DTS) as well as Dolby EX tracks, assuming the EX flag doesn't force it to use EX decoding.