In allowing people to vote up/down, I realized that there needed to be a separation between 'Yes this quote is accurate' and 'Yes I think this quote is important', since the two can be exclusive.
In the end I decided to implement a two-step process. The first step is to Agree/Disagree with the quote at hand. Once a user has voted in this way, they have an optional second step to vote for how 'Important' the quote is (important or unimportant).
I have yet to see how it will work out, but I'd love any comments you guys could provide.