Homage/Influence

Recent events and my WIP have coincided (funny how that happens, lol) and I have a question about paying homage to certain authors and their affect on culture, compared to "stealing lines".

How much is (or is any) too much? I will explain the thought that brought this on, so that maybe it is more clear.
In my regency era novel there are multiple murders, and the main motivation is inheritance. While writing the "murderer revealed" scene, I was sorely tempted to have an MC mutter "And then there were two." Obviously this is not a historically relevant quote, as my story is set long before Agatha Christie, but it is a sign of how pervasive such a phrase has been, and her impact on me and my writing. So...where does homage begin and end, and where does plagiarizing pick up? Is a line, both acknowledging their influence and greatness, a tribute, or is it stealing? Just curious what everyones thoughts are.

ha! that sucks...I had this David Gemmell chapter in mind...
I never thought about the character name route..that's a good idea though. I search endlessly for the perfect name for the MCs, and then my secondary characters get relegated to the "whatever I can think of or name generate quick enough that I have no intention of using soon for any type of story" pile.