switching formulas

So my milk has not been coming in as quickly as I hoped after my emergency C section a couple days ago. My doctor is telling me to formula feed as well and breast feed even the smallest amount of breast milk I can pump out. The hospital had given me a gerber brand but I want to try and switch to earths best organic because I have researched a lot on it and it's the closest to breast milk as they can make it. Is it safe to switch formulas? Has anybody done this and what is the outcome?