I've only got First Contact (assuming we're talking about the movies here -- the first season's due out in March). I have watched it before using 6.1 without problem. If it's displaying both DD and DPL and will not let you use 6.1, I'd check first to see if the DVD defaulted to Dolby 2.0 instead of 5.1 (a lot of discs with both 2.0 and 5.1 tracks default to 2.0 because that track generally decodes better for receivers that only have DPL). A Dolby 2.0 soundtrack would be Dolby Digital, but would also rely on DPL decoding to get surround. It also would not be able to use the 6.1 decoding.