Prepare rice mixes according to package directions. Melt butter in a large skillet over medium heat; add celery and onion. Saute 10 minutes or until tender. Stir in water chestnuts, rice, chicken, 3 cups cheese, and next 5 ingredients.
Spoon mixture into a lightly greased 15x10 baking dish or a 4 quart baking dish. Top casserole with breadcumbs. Bake at 350 degrees for 35 minutes. Sprinkle with remaining 1 cup cheese and almonds; bake 5 more minutes.
You can divide this casserole evenly between 2 11x7 baking dishes. Bake as directed above or freeze casserole up to 1 month. Remove form freezer, and let stand at room temperature 1 hour. Bake, covered, at 350 degrees for 30 minutes. Uncover casserole, and bake 55 more minutes. Sprinkle with remaining 1 cup cheese adn almonds, and bake 5 more minutes.