Hmmm, I get the conundrum. You are happy now but would you like an immersive setup.
So, "pre-outs" allow you to connect an external amplifier to the receiver. You have an external amp so these would be needed. Pre-outs are offered in receivers for subwoofers, and sometimes for the 5 or 7 channels that are typical for surround sound. These 5 or 7 channels are called "bed channels". Your "height channels" could be connected directly to the receiver so using an external amp wouldn't be necessary.
FWIW I have an auro 3d setup in my media room and an atmos setup in the man cave. I don't have a dedicated theater and the man cave is really small.