I have the older Oppo 105 and 105D (which aren't 4K), but use them to switch between various inputs. My 105D takes my DirecTV signal via "HDMI Back" and has two HDMI connections to my Yamaha RX-A3000, one for audio and one for video. My Panasonic Plasma is then connected to the A3000.
I found that the Darby processing on the Oppo of my DirecTV signal gave me a better picture.
Upstairs I use the front input of the 105 for my Apple TV. Audio from the Oppo goes to Sennheiser wireless headphones and video goes to the TV.
I use a Harmony remote to switch inputs on both Oppos if I want to play a Blu-Ray
I have never experienced any lip synch issues, even through the longest path: DirecTV > Oppo > RX-A3000 > Panasonic Plasma.
As others have said about their receiver, my a3000 does just fine with the audio. Obviously it doesn't do 4K switching. It also doesn't do Atmos (I think they didn't update the model to support it - although it is a 7.1). Not sure if I want (or can) do Atmos, so I can wait a while before I replace it, since it cost about as much as the TV.
I'm waiting for the closeout prices on the 2017 LG OLEDs when the 2018 OLED models come in. I'm not that interested in the improvements in talking to my television, as per the preliminary comments about the new LG models at CES last week. My current interest is in the
LG OLED65E7P which was $5k in June, went to $3999.99, and is now $3499.99 at Best Buy. A a drop of a few thousand more and I'm in!
Since sound quality really matters to me, rather than replacing my Yamaha RX-a3000 I'll just replace my 105D with the 205. If you look at audio bitrate numbers for 1080p Netflix and Amazon Prime (and I think iTunes) movies they are in the 300 Kbps or less region, and this is for 5.1! [I assume it is the same for UHD. If someone has the developer HUD installed on their 4K Apple TV I'd love to know what numbers they get when streaming UHD content!].
The only way that I know to get decent audio (DTS-MA) on a 4K source is with a UHD disk, so that means I pretty much have to replace the Oppo to get a 4K blu-ray player. I also want that headphone jack and MQA support (which the 203 doesn't have) so that means the 205.
So my plan is to connect my Apple TV to one of the Oppo 205 in ports (either "HDMI front" or "HDMI back"), and DirecTV to the other. The Oppo will send the audio to the Yamaha, and the video to the LG OLED.