I get where you're coming from as the 2510 are a really good speakers as are the KK2012 subs.
I would go and have a proper demo of some Atmos set ups to see if it is something that impresses you. I have to admit that the first few demos I heard I was pretty underwhelmed after all the hype. I still don't think it's the big deal that some have made out, though I've ended up with this set up almost by default. NOTE: I used to have my surrounds very high up, so I'm not particularly 'wowed' just because sounds come from above me...
What I would say is that with such decent LCR speakers I wouldn't think that putting some very cheap ceiling speakers will add anything much at all. The demos I heard with these kind of set ups were the more underwhelming ones IMHO.
I can't help on the processor front either; while I own an AVR390 I can't see (apart from balanced outputs) much advantage to the AV860 over it. I use my AVR390 as a processor and don't have any issues about noise, so any claim of better power supplies reducing noise, etc seem moot to me. You could get more variance to the sound due to different Dirac calibrations/target curve settings I reckon. However, since the bass management has been found to be in the wrong place in the signal chain I would hesitate to recommend the Arcam right now. While ARC perhaps isn't as good as Dirac at least Anthem put the bass management in the right place.
Many thanks for taking the time to reply with an honest detailed answer.
I think i'll abandon the in ceiling speaker plans for now, the wiring is in place should i decide to add some later.
I guess my next decision then is which processor / receiver to go for.
The reason i am leaning towards a processor is the simple fact i have no need for extra amplification, plus the fact that i'm led to believe a processor runs cooler than an amp / receiver, something i have to take in to account due to limited space where it has to go.
I've read both the Arcam & the Anthem posts & feel the Anthem has less issues associated with it, neither are cheap & now you've got me thinking should i just opt for a cheaper receiver (Anthem or Arcam) rather than the processor variant, i guess it may come in handy if i decide to go for in ceilings as that could then power them also..
I sometimes hate this AV game...
Another thing i've thought about & perhaps someone with some experience could advise, would keeping my current processor (Onkyo 5509) & adding something like the Dirac Live processor enhance my set up, or is the Onkyo a bit long in the tooth now?
Would an up to date processor / receiver be the best route.
I'm not overly unhappy with my processor, i guess like most people when something new comes out & gets rave reviews, all of a sudden you feel like you're missing out..
Thanks in advance.