RD, your player, rather than your receiver, should handle the situation. When you set the bass management for the multichannel analog outputs on the player, the center speaker will be set "none". The player should then mix the center channel(if present; not all SACDs have one)equally into the left and right speakers, resulting in the center channel material being played as a "phantom" center, as usual.

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Enjoy the music, not the equipment.