In a small bowl, combine paprika, pepper, sugar, celery salt, salt, cayenne and mustard. Rub seasoning mixture over sausage. Grill according to package directions until heated through, turning occasionally. Meanwhile, cook macaroni according to package directions.
In a large skillet, melt butter over medium heat. Add cream and onion; mix well. Bring just to a boil, stirring occasionally. Reduce heat; stir in cheese. Continue to stir just until cheese is melted.
Drain macaroni; add to cheese mixture. Cook and stir until heated through. Season with salt and white pepper. Serve with grilled sausage.