My Denon receiver overrides my stereo setting if I put in a multi-channel media. I've never tried to put it back to straight stereo unless the media also included a stereo track (which you would have to choose from the media's menu).
I'm like Mark. On my receiver, I am pretty sure "Stereo" would result in fronts only plus LFE to the sub. "Pure Direct" would give me fronts only, no sub. Definitely not center in either case. However, I'm not sure I can even choose either of these when using a multi-channel source. Although, it's possible that I just never tried.
What would happen if you force a multi-channel media into stereo mode? I assume that if you can do it, it must be smart enough to blend the surround and LFE tracks into the main left and right.
Mostly just thinking out loud at this point.
