Huh. My receiver only has two optical inputs on the back, but the TV will make my third source. I hadn't though about that. It has another optical input on the front, so I can make it work. I guess that I'll just plug my MacBook audio into the front of the receiver when I want to watch Netflix.
Too bad my DVD player doesn't also have a coax output. It's the only one of the three that I own that doesn't (but it's better overall than the other two, so I'll leave those boxed up).