I know what you mean, I'm only using two of the Anthem channels for atmos, I have a 7 channel power amp doing the rest. I would love the AVM 60 but it's ridiculous money. It's annoying how AV processors cost more than a AV receiver despite having no power amps inside.
You could also look at Emotiva, I have no experience of them but they are meant to be good for the money.
The anthem avr is not bad with few channels driven but with 5 xhannels driven power output is reduced a lot and I think they don't even give all channels driven?
I have 200w X 7 so stupid getting avr unless left over for Atmos but as I said I have four , two channel power amps so I'll use them
Stupid prices for AV pres I have a second hand lead..new £4500. Insane