In a large bowl, beat cream cheese and mayonnaise until smooth. Stir in the cheeses, garlic powder and seasoned salt. Spread 5 slices of bread with the cheese mixture, about 1/3 cup on each. Top with remaining bread. , Butter the outsides of sandwiches. In a skillet over medium heat, toast sandwiches for 4-5 minutes on each side or until bread is lightly browned and cheese is melted.