Keep the 2 channel as is and connect the OPPO and Cable box to the Anthem. Connect the Anthem to the ore with interconnects. The rest is using the Anthem's menu to configure which speakers are connected. I'm assuming your pre has a home theater bypass because it worked before. Or you just bypassed that and manually did it. I see both ways will work.
Good luck, I'm just passing along what I've learned from here. Someone can correct any misinformation if need be.
Good luck, I'm just passing along what I've learned from here. Someone can correct any misinformation if need be.