Ahhaa that's the tricky one.
At the moment I'm using my oppo105 as pre with analogue outs to oldie but goldie sherbourne seven channel power amp,
But Dtsx and Atmos are calling and I'm just dipping my toe to see where to go
Best solution for an avr is the Marantz 7010 @ £999 which does 9.2. it's getting the DTS X update next week and use it as a processor for 11.2 channels using your sherbourne for the 7 bed channels and the marantz for the 4 heights.