The only issue I'm havning right now is that the Atmos channel crossover setting gets reset every time I turn off the AVR. This is a known issue though and will be patched in the next firmware update(Arcam is slow with their updates though and I feel like they are losing A LOT of potential just due to having a bad dev setup). I run 4k and Atmos and I have no issues with playing stuff. DTS:X, Atmos is all good. The only real alternative, like that has been mentioned, is the NAD but there has been a bunch of hardware issues with those units and still quite a few bugs from what I'm reading. Doesn't seem like they fixed DTS:X support yet either. But their real strength is that they run "proper" crossover slopes for the BM and you can select different crossovers for all speakers.
In terms of bass management for the Arcam the limit is that all the speakers in the base layer needs to use the same crossover frequency and all the speakers in the Atmos layer needs to use another one. If you need to have different crossovers for your speakers that can become an issue. Other than that these Arcam units are really solid quality. AVRs are complicated things and all avrs will have their own issues so pick your poison.
Room| Treated | Sound| Front: Ino Audio i32s, Center: Ino Audio i16s, Surrounds: 6 x Ino a2, 6 x Ino a1, Subs: 6 x Ino Infra-Y|
Picture | Epson TW9300, Seymour Center Stage UF 130.4" retractable 2.35:1 |
Electronics | Arcam AVR390(Dirac Live), 3x Ncore nc400 monoblocks, Emotiva XPA-2 Gen2, EP4000, Panasonic UB700, Allo Katana + Isolator 1.2(Roon bridge/DAC), ATV 4K |