Place potatoes into a large pot and cover with salted water; bring to a boil. Reduce heat to medium-low and simmer until tender, about 20 minutes. Drain.
Transfer potatoes to a large bowl and mash with cream cheese and sour cream until thoroughly combined; slowly mash in chicken broth, followed by garlic powder and salt.
Beat potatoes with an electric mixer on high speed until whipped, about 2 minutes. Transfer potatoes to a slow cooker. Set slow cooker to Low and cook for 3 hours. Stir melted butter into potatoes just before serving.