Thank you for your advice everyone. It's very helpful to hear different perspectives. My undergraduate background is qualitative (anthropology), but most of the work I do right now is quantitative, survey research. I feel pretty strongly that not enough thought is given to how qualitative and quantitative data can be used together. It's a specific goal, but if I'm going to take the time to get a PhD then I want it to get me the things I want. Looking to see who's publishing on mixed methods in the social sciences seems like a good starting place, in addition to searching department websites for faculty.
To @rising_star, I am considering whether other types of degrees will get me where I want to go.