Two amps into one pair of speakers

I'm guessing from the OPs description that it's not an issue as long as they are not both sending a signal that it's two amplifiers connected in parallel and not a bi-amp setup.

I have a home theater receiver and Pathos integrated connected to my speakers in parallel, but I have an intermediate toggle switch in the speakers cables so that only one amplifier can send a signal to the speakers at any given time.  The custom switch even has a resistor to provide protection during the switch since it was first used with an all tube amplifier that needed a continuous load.

Before I got my custom switch built by an EE friend (it's setup to protect a tube amplifier at all times), I used 10AWG Blue Jeans speaker cables with the welded banana plugs and just swapped cables back and forth with my home theater receiver.  I'm still using the switch and it's the barrier to upgrading speaker cables as there's more cables required and a clear sub optimization in the setup.