In some ways, the best bet can be an atmos cheapie receiver, that has preamp outputs. And the amps having inputs, of course. But,. of course, the whole atmos thing is just an attempt to stay alive and get you to buy new again..well..again. and again.
To look at surround sound, as a business, it makes the merry-go-round of stereo audio, look like a bunch of incompetent pikers. the kind of pikers who can't get their buyers to constantly buy new. There are so many dang surround components being thrown and tossed, just to get to the new unsupported no software format, it makes stereo audio upgradeitis look like child's play and level headed sanity.
To buy a new processor for a bunch of movies that are not here, in a market that is trying to eliminate physical media and the reason to have atmos outside of actual theaters. Theaters which are dying off.
So, to not play the game so much, go for a cheapie atmos unit that has preamp outs and add that in..purely for the preamp function. Just the way I would go. Seperate amps, upgrade the processors, by buying the best mid to low cost receiver that has preamp outputs.