Rinse fillets, and pat dry; sprinkle with 1/2 teaspoon salt and 1/4 teaspoon pepper. Place in a greased 13- x 9- x 2-inch baking dish. Combine wine and water; pour over fillets. Bake, uncovered, at 400° for 12 minutes. Drain, pouring liquid into a glass measure; let solids settle. Reserve 1/2 cup clear liquid.
Saute mushrooms in 2 tablespoons margarine and 1 tablespoon lemon juice 3 minutes or until tender. Stir in 1/4 teaspoon salt and 1/8 teaspoon pepper. Spoon over fillets.
Saute celery, green onions, and crushed red pepper in 1/4 cup margarine in a saucepan over medium-high heat until tender. Add flour, stirring until smooth. Cook 1 minute, stirring constantly. Add whipping cream and 1/2 cup reserved liquid; cook over medium heat, stirring constantly, 1 minute or until thickened. Remove from heat; stir in parsley, white pepper, 1/2 tablespoon lemon juice, and 1/4 teaspoon salt. Spoon over vegetables and fillets; sprinkle with cheeses. Combine 2 tablespoons margarine and breadcrumbs; sprinkle over casserole. Bake at 400° for 15 minutes.