The one and only time I've seen my male panther fired up was to impress my female the first time he saw her. I was so annoyed because he climbed up to the top of his tree and was mostly hidden behind the foliage when he did it, so I couldn't really see him in all of his glory. I've never seen it again since then, not even when I showed him the female for the second time. I've never tried the mirror thing though, and probably never will.
I have an Ambanja, and he does get a little fired up, but I still can't get him to fully fire up. He could care less about a mirror, and I have two other chams now and he doesn't even get excited about them. For some reason, when my daughter goes to take a photo of him with her iPhone, he tends to get a little excited, and that's the only time. Some chams are easy, some just are very laid back.
I could probably really stress him out to see his true colors, but I just won't do it, maybe it's just me but I like him just the way he is... With spring coming I hope to get him outside more, maybe he'll fire up then..