Arrange 25 to 30 crackers on the bottom of a 9x13" pan. In a saucepan, mix butter, milk, both sugars and graham crackers. Bring to a boil and continue stirring while boiling for 5 minutes. Pour 1/2 of the mixture over the crackers and spread out. Arrange another layer of crachers over the mixture. Spread the other 1/2 of the mixture over the crackers. Arrange another layer of crackers. Melt both chips and peanut butter together and stir. Spread over the top. Refrigerate about an hour. Cut into squares.