Melt the butter in a large pot over medium heat. Add the marshmallows, and stir often until they're melted. Take off the heat, and stir in the peanut butter. Mix well. Add the Rice Krispies 2 or 3 cups at a time. If you want them to be more on the chewy side, add 7 cups. If you want them just a little more firm, add 8 total cups! Pour in the bag of peanut butter chips, and fold them into your Rice Krispie mixture. Some of them will melt, but you want some to stay whole.