Preheat oven to 400°. Prepare and bake muffin mix according to package directions. Cool completely and crumble; transfer to a large bowl. Add 1 envelope taco seasoning, eggs, 1-1/2 cups enchilada sauce and meat; mix lightly but thoroughly. Shape meat mixture into 1-1/2-in. balls; bake on greased racks in 15x10x1-in. baking pans lined with foil until lightly browned, 10-12 minutes., Place meatballs in a 5- or 6-qt. slow cooker. Combine remaining enchilada sauce, salsa, chiles, 1/2 cup cheese and remaining envelope taco seasoning; pour over meatballs. Sprinkle with remaining cheese. Cook, covered, on low until meatballs are cooked through, about 3 hours.