I understand what matters is the quality of the sample work and the SOP, not much else. Basically the idea is that people want to see some kind of spark that says you can do original research rather than be a very good student who does the right things and stops there. This, of course, is only an ideal expectation. In reality, I have seen extremely odd decisions made. I do not know what you have in mind when you say your GPA is not good, if it is really too low it might make professors think you are not committed. Also depends on what classes are not so good.
My MA GPA is not great. But I've done good research and presented it, thought not published yet.