I think I get what you want to do because I’m planning at some point to do something similar. It blows my mind that a lot of companies have “home theater” pass throughs but never do they have sub inputs and outputs which is nuts as subs are critical to home theater. Maybe they assume you won’t be using subs for two channel which I think is also silly. Take a look at the JL Audio cr-1 crossover and see if that does what you need.
AV Receiver with Integrated Amp - Sub Connections?
If I want to have the sub work with my receiver while watching movies and also the integrated amp while listening to music, how do I connect the sub to both the AV receiver and integrated amp?
Also, will this not work since an integrated amp doesn’t have a crossover setting for a sub?
Also, will this not work since an integrated amp doesn’t have a crossover setting for a sub?