Irek

Do you have a separate budget for other components ?

It's a desktop dac so no point to compromise sound quality with wireless connection. Usually headphones or speakers comes first with matching amplifier. Sometimes that amp has a DAC build in.

My Yamaha AVR when connected to bluray player displays Dolby Atmos in the centre part of the screen (no extra logo). However sometimes it's "forgetting" to switch to dolby atmos, I am pressing the straight button on remote control to remind it.

Depends on headphones it might be better to get DAC/amp combo. USB is the connection to use. Topping, Schiit, Ifi are quite popular at that price range.

I would move that couch forward 1m or more if possible. I think 5.1.4 or 5.2.4 is plenty for your space.

Aria 906 is really good at it's price but if you jump to 4k than there are other options as well. If you go with Aria I would consider adding subwoofer, maybe Rel T7i. Second option would be PMC 25.21 Third would be Osborn Eos with focal driver. It's hard to say how they are going to perform, you might be able to borrow them even for a few hours to audition at home. there is an option of in wall speakers as well, you basically cover the face of bookshelf with MDF and cut a hole for in wall speaker (little bit of carpentry/joinery). something like Focal 300 ICW 8 In-Wall.

How that apple TV is connected? Are you using 4k hdmi from Apple TV to AVR and another 4k hdmi from AVR to TV?

Yes, it's 7.1 or 5.1.2. Only 5.1.2 is Dolby Atmos and the Avr should display Dolby Atmos logo. It may not always automatically detect Dolby Atmos. Those upfiring speakers need to be connected to front presence. Nothing is wrong with 5.1.2 unless you have a very large room.

I would try class D power amp, maybe Primare A60 .

I would audition speakers + amplifiers as a combo within my budget. Then I would narrow my choices base on room size and preferences to 3 brands of speakers and amps. Than I would try to audition those combos at my listening room. Also I wouldn't look at amp's different features, any DACs, streamers, EQ, room correction, it can be add later. Sound is the priority.

That door can be converted into sliding/hanging door.

If you like Topping they should have soon MQA DAC. I might be worth waiting for.

Have you try to move one or more panels behind speakers? They should help to absorb reflections from back and side walls.

Nothing wrong with PMC 25.23 I would add acoustic panels behind speakers and maybe speaker stands. https://www.soundseasy.com.au/products/primacoustic-london-8?variant=914795933&currency=AUD&gclid=Cj0KCQjw6_vzBRCIARIsAOs54z7jrQyaroxN1WfDYMMaPv5894sfnx8gFtp1NfzxuKvjYV8PcE2hj58aAqqGEALw_wcB

Do you mean Rotel RA-1572 Integrated Amplifier? It's not class D amplifier. The class D amplifiers are not digital, unless you mean amps that convert all signals into digital for processing.