I’ll quickly clarify myself…

You may be able to find Shakespearean subtexts in P&P, but that is not the point I was making. I was saying that Darcy intentionally paraphrases a famous line from “Twelfth Night”. Sure, he replaces music with poetry, but the idea remains intact.

When Elizabeth inquires “I wonder who first discovered the efficacy of poetry in driving away love!" Darcy answers "I have been used to consider poetry as the food of love,". If you are not familiar with the reference it sounds as though he is contradicting her by suggesting that poetry is necessary for love. However, considering the following:

If music be the food of love, play on;
Give me excess of it, that, surfeiting,
The appetite may sicken, and so die.
–Duke Orsino, Act I, Scene I, Lines 1-3

Darcy is agreeing with Elizabeth by invoking lines from a character who wishes music would drive away love.