Place the broccoli florets, cheddar cheese, cranberries, bacon, sunflower seeds, and diced red onion in a spacious mixing bowl. In a separate smaller bowl, blend the mayonnaise, sour cream, white wine vinegar, sugar, salt, and pepper until the mixture is smooth and homogeneous. Drizzle the prepared dressing over the broccoli mixture and thoroughly combine by tossing or stirring to ensure even coating. Though it can be served immediately, allow the salad to chill in the refrigerator for at least one hour to let the flavors meld. Stir well again just before serving. Keep refrigerated if not consumed immediately.