Add a/b switch? How to run 2nd pair of speakers?

I've got speakers in both my living room (main system) and kitchen. I used to have an integrated that had an a/b switch so it was no problem playing both or either sets of speakers.

Now I have moved up in the world and purchased a Rogue Tempest Magnum integrated which obviously does not have an a/b switch.

What are my options to keep my kitchen speakers running? I do not want to set up a seperate system. But, I've heard piggy-backing the speaker terminals degrades the sound.

Does adding a seperate a/b switch effect sonics negatively?
Where might I get one and what is a good brand?

Any ideas? Thanks very much.