I think the best quality will be RGB/HV (or component) to the middle of the back of the avant. You'll need to select a preference for the audio input. You'll need to turn off and unplug the Avant after making the connections. Then, be sure that the new *source* is outputting before turning on the Avant again (This input will *see* the signal only this way). Make other menu adjustments for the selected input, and things should be as good as they will get.
Other Beoworlders, correct me if I'm wrong.
Barry