According to what I'm reading on the Toshiba site, those DVD players only support 5.1 audio in either HDMI or analog output. However if you use the standard S/PDIF coax or optical you will get whatever is on the DVD (which could be DTS 6.1 or DD EX), except the new audio formats.

The advantage I see you getting using the analog output or HDMI audio is if the DVD is encoded in the new audio formats, but only 5.1.

Can the 990 do Dolby PLIIx on the 5.1 analog input? If so then it will expand the 5.1 input into 7 channels.