Batteries (alkaline) are very cheap on sale @ your local Walmart store.
...And nowadays they have some pretty good rechargeable batteries. Get two sets and you're probably set for life.
Me, if I was you (very simple) I would get the Denon X5200W receiver with XT32, Atmos, and Auro-3D upgrade.
Or, even better; I would wait for second gen receivers. ...From Denon/Marantz. ...Or a pre/pro from Marantz.
Then, you can always add the MiniDSP later on, with integrated Dirac Live. ...Just to check things out, for fun.
That way you can still use your maleficent 805 for a little while. ...Till we seriously get some software (Atmos/Auro). ...Couple years or so, @ this pace.