No, you can't. The reason is that you will have the amp's output impedance in parallel with your speaker AND the other amp's output impedance. This will cause too many issues to be useful.
I assume your Sansui has crappy wire jacks for the speaker leads. If you can adapt them to bananas and use banana terminations on your speaker cables, it will be easy to just swap amps when necessary.
Look to see if your Sansui has pre-out jacks so you can just run it to your Cary preamp and have the tuner that way. Some receivers had pre-outs and others didn't so you have to check. This would be the cleanest (assuming your Cary has two extra inputs for both the tuner and Sony/Lite).
Arthur
I assume your Sansui has crappy wire jacks for the speaker leads. If you can adapt them to bananas and use banana terminations on your speaker cables, it will be easy to just swap amps when necessary.
Look to see if your Sansui has pre-out jacks so you can just run it to your Cary preamp and have the tuner that way. Some receivers had pre-outs and others didn't so you have to check. This would be the cleanest (assuming your Cary has two extra inputs for both the tuner and Sony/Lite).
Arthur