One amp would be for my 2 channel system and the other (a receiver) would be for my home theater system. So long as I’m not powering both amps at the same time, is it safe/ok/advisable to connect both amps to one pair of speakers?In one word NO!!
As one of the amps will be trying to drive the others output stage, even if not on.
Unless both amps have a speaker terminal disconnect relay when not on for both + and - terminals, only a tech will be able to tell you.
Cheers George