Your gear list answers half of this already. A 77-inch C5, an Onkyo doing the decoding, Klipsch 800s up front with the 500SAIIs pulling double duty for heights and rears, and a 12-inch sub. That is a system that will show you the difference between a good handoff and a bad one, so the question isn't really which box, it's how you wire it.
Roku Ultra, Google's 4K streamer and Apple TV 4K all do Dolby Vision and all do Atmos. On a spec sheet you are choosing between three boxes that check the same two boxes. Where they separate is app behaviour and how stubborn they are about output. Apple TV lets you lock the output format and match content frame rate and dynamic range, which on a C5 means you stop the set renegotiating HDMI every time a trailer ends. Roku's interface is the fastest to hand to someone else in the house and the hardest to keep clean, and I would not build a reference chain on it. Google's box sits in between and its ad surface has been creeping.
Not owning Apple gear costs you almost nothing here. No iPhone means no handoff and no AirPlay from your own phone, that's it. The tvOS box does not require you to have anything else.
The part I'd actually plan first: run the streamer into the Onkyo, not the TV, and let the receiver hand video up to the C5. Going into the TV and relying on eARC back down works, but it's the setup that generates the Atmos-dropped-to-5.1 threads. Anyone here running the opposite way on a C5 with no trouble?
Roku Ultra, Google's 4K streamer and Apple TV 4K all do Dolby Vision and all do Atmos. On a spec sheet you are choosing between three boxes that check the same two boxes. Where they separate is app behaviour and how stubborn they are about output. Apple TV lets you lock the output format and match content frame rate and dynamic range, which on a C5 means you stop the set renegotiating HDMI every time a trailer ends. Roku's interface is the fastest to hand to someone else in the house and the hardest to keep clean, and I would not build a reference chain on it. Google's box sits in between and its ad surface has been creeping.
Not owning Apple gear costs you almost nothing here. No iPhone means no handoff and no AirPlay from your own phone, that's it. The tvOS box does not require you to have anything else.
The part I'd actually plan first: run the streamer into the Onkyo, not the TV, and let the receiver hand video up to the C5. Going into the TV and relying on eARC back down works, but it's the setup that generates the Atmos-dropped-to-5.1 threads. Anyone here running the opposite way on a C5 with no trouble?
