MastersToPhd

Hi guys, So I am currently a recent Masters student thinking about applying for PhD next app season. I am somewhat worried about my grade currently. I am hovering around 3.5 right now and might do a bit better this semester. My undergrad GPA is around 3.75. Both programs are competitive and top 20. I am a full TA so time is limited. I have to decide how to balance my time. With my current schdule, my GPA after this semester and before applications are due will probably hover around 3.5 - 3.6, much lower than I hope to achieve. On top of classes and TA duties, I want to get started with some research as well on the side with a professor who's research interests me a lot. So my question is, for general phd admission to top 20 programs, should I spend more time doing better in my classes or should I just not worry about grades and invest in research (keep A- / B+).