RCA line level switcher to allow dedicated two channel stereo and multichannel surround

My audio system has always been multichannel surround built around a digital home theater processor. What I'd like to do is isolate two channel sources from multichannel sources and run two channel stereo CD player/DAC and turntable/Pearl 2 phono pre through the Iron Pre I'll be building and leave all the multichannel audio (TV, bluray, roku, etc) to the current surround processor while utilizing the same amps and speakers at all times.

A line level switcher would allow this, but currently my passive sub is driven by the processor as I'm utilizing all the xover and eq controls there so that complicates things. I could ignore the sub controls on the processor entirely and instead run the sub via MiniDSP for instance but I'd like to avoid that.

Surely I'm not the first nut to do this without wanting to unplug/plug RCA cables each time. What solutions have others created?

For reference current front end is B&K Reference 50 S2 driving dual mono PassDIY F6 for left and right speakers, a monoblock F6 for center channel speaker, a Crown XLS1002 for passive sub and a B&K AV2500 for surrounds. Main speakers are DIY Bordeaux, center is DIY Statements center, sub is DIY Dayton Ultimax 15.
 
There are 3 channel video switchers for 2 to 4 inputs to 1 output. They have RCA jacks. They cost about $12 on ebay/amazon/aliexp about double in stores. Look for the red, white, yellow inputs. The yellow is video, but you don't have to use it. If you use the yellow for sub, red for right, white for left, there you are.
 
you can use a pair of y splitter connect to the Pearl 2 output, one of the y splitter output go to one of the line level input of the B&K processor for subwoofer processing, the other output of the y Splitter go to RCA switcher.
There will be both the Pearl 2 output and a cd player/DAC on the two channel side. Using a y splitter from each to the B&K processor means that the processor also must have the correct input selected in addition to selecting an input on the 2 channel preamp. Perfectly functional but I wonder if I'm overlooking a more elegant solution?

The solution above is the only one I can see unless I run the sub as a strictly two channel system via the left and right preamp outputs using MiniDSP or some other external subwoofer xover/eq box.
 
Through the processor your main speakers are typically high passed. Do you want the same through the preamp? If so I would add a 6-24 crossover, to keep the signal path analog, after the preamp then add a multi-way switch to switch before the amps.
 
Perfectly functional but I wonder if I'm overlooking a more elegant solution?
How about put it in your preamp, use a switch for "home theater pass through" and a set of subwoofer output.

Coda CSiB
Screenshot 2023-06-02 at 22-15-04 CODA_CSiB_Integrated_Preamp_Amp_Destination_HiFi_Rear.jpg (W...png