Clarence, this one has gotten a bit tangled-up in terminology or possibly in a misunderstanding of some of the modes. When you mention 5.1/7.1 you're apparently referring to the mode that simply sends the left side stereo to the left side and back(if present)surrounds and likewise for the right side. It applies only to stereo material(useful for parties, etc. to have the sound more nearly the same all over the room)and has nothing to do with 5.1 DVDs.
As I suggested, since you've paid for a receiver and speakers which can "liberate" the ambience imprisoned in the 2-channel format and steer it to the surrounds where it belongs, you should use this capability. This means that you couldn't use any stereo mode such as direct, pure or stereo itself, since DPLII(or Neo:6 which Ken prefers)is an entirely different processing mode. Experiment.
