6pm.com is owned by Zappos. All of the products I have purchased have been authentic, including Patagonia. I seriously doubt that any products sold by a Zappos owned company would be anything but authentic.
Hi Reagan, no, none of the brand name stuff is fake. I bought some Patagonia things a couple of months ago, and was really happy with the things. I truly think you will like 6pm too. Good luck.