bad to mix amps?

Yes, you can do that. It can produce issues with mismatched volumes but in most cases that would be minor after correction software. 

IMHO, no it does not really matter for movies and TV. As long as the amps meets the power requirements of your speakers as well as their sensitivity and load, it should be fine. I have tried different amps for HT duty and the first thing you notice is that the new more powerful amp makes the speakers really pop. But of course this is prior to level matching or running any room correction. Once that is done, the differences between amps (that have correct specs) is smaller than one might think for HT duty. Amps for 2CH music is a different story.