Just adding my voice to the choir, but I'm headed to Baylor College of Medicine PhD in the Fall, and my cGPA is a 3.1. I had great letters of rec, an okay GRE (167 verbal/156 quant), one first author publication, and three years of research. No interim years as a research tech and no masters degree. I did start a company, but most people I spoke with on the interview trail said that while my work experience was interesting, it was not the thing that got me there. I did end up getting shut out from the "top-tier" programs I applied to (e.g. Stanford, UPenn), so if a top five is your singular goal then maybe a masters is in order, but I had interviews at Baylor, Dartmouth, and Brown, which I think are pretty well regarded depending on the program.
Just make sure to knock your SoP out of the park and you'll be fine!