Comment by mikepurvis

... that said, there is also a small market for "separates" where you have a decoding-only preamp that either feeds active speakers or another box containing just the multi-channel amplification:

https://www.marantz.com/en-ca/category/av-separates/

The output of these units is line-level signals feeding high-impedance loads. They could definitely be a fraction of the size they are.