Available AVRs:
Denon AVR-X4700H $1,700
Denon AVR-X3700H $1,350
Denon AVR-X2700H $950
Marantz SR6015 $1,500
Marantz SR5015 $1,120
Marantz NR1711 $980
Yamaha RX-V6A $675
Yamaha RX-V4A $540
The model I recommend if you can afford it, is the Denon X3500H or X3600H or X3700H, which have Audyssey MultEQ XT32. This is state of the art digital room correction, which is way better than Audyssey MultEQ XT, that all lower models have (models like X1500H, X1600H, X2500H, X2600H, X2700H, etc). All models above this (ex. X4400H, X4500H, X4700H and so on) have this too, but cost higher, with the benefit of more channel processing.
Amir reviewed the following Denon:
X3500H
X3600H
X3700H
X4700H
As you can see, they're all recommended.
So any of these will suit your needs. Although, seeing how you're looking for 8K support...only the latest models would be needed.