In a skillet, cook beef, onion and garlic over medium heat until meat is no longer pink; drain and add spaghetti sauce, salt, oregano and brown sugar, to taste.
Spread 1/4 of the meat sauce in an ungreased 5-quart slow cooker. Arrange 1/3 of the noodles over sauce, breaking noodles if necessary.
In a medium bowl, combine cheeses.
Spoon 1/3 of the cheese mixture over noodles.
Repeat layers twice, topping with remaining meat sauce.
Cover and cook on low 4-5 hours or until noodles are tender.