Hi,
Usage: Movies/Music 50/50
not a gamer, don't need hdmi 2.1
neither has Dirac so that doesn't matter.
existing speakers 5.1 PSB Image + 2 Pairs of Image for overheads Atmos/Auro3D.
no chance to demo where I live, but an order via a dealer.
at same price which is Sonically better ?
Thanks.
If you believe, like many people do, that there are audible differences between AVRs that have specs and measurements that indicate they are transparent, then there is no alternative to doing your own audition.
If you do believe in specs and measurements, then I would suggest you just choose based on the features you need, aesthetic, and price.
To me, the SR8015 wins on:
Room EQ/correction:
- Processing capability: 13 channel vs A6A's 11 channel
- Aesthetics: Highly subjective so ymmv.
The Yamaha wins on:
- Much better DAC specs, only slightly better than the SR8015 manufactured prior the spring of 2021 but much - better than those made after D+M switched to the PCM5102A DAC chip.
- Reportedly it runs cooler.
- Based on track record, it may be better in terms of reliability (no one knows for sure).
- Has an extra foot.

Only a + for people prone to marketing hypes
So, to your question on "sonically":
1) If DSPs are not used, in a blind test, no one should be able to tell a difference between those 2.
2) If DSPs are used, for sure they will not sound the same, all else being equal, but it is not possible to say which one will sound better, only you can tell, because it is a 100% subjective thing.
*3) The Yamaha has an edge regardless, based on measurements if you use it with worthy external power amps.
*4) The Marantz has the edge if used as AVR, based on Gene's measurements of the A6A and the SR8015.
* 3) and 4) are theoretical, ie. on paper only, because either one's specs and measurements indicate in DBT, controlled listening tests, both are transparent enough such that normal humans will not be able to tell them apart under most normal listening conditions if and when both are not not push to near their output limits. Also, it is based on not using DSP functions, if used, it becomes a subjective matter, in that case, again, only the user can say which one is better sonically.
For me, if I were forced to choose one now, I would take the A6A, but only because I am OCD on DAC chips.