In a large bowl, gently toss the 6 cups of mixed berries with 1/4 cup of granulated sugar. Let the mixture sit for about 15-20 minutes to allow the berries to release their natural juices.

In a separate large bowl, use an electric mixer to beat the 8 ounces of softened cream cheese until smooth. In another bowl, whisk together the instant vanilla pudding mix and 2 cups of cold milk until it thickens (about 2 minutes). Add the pudding mixture and 1 teaspoon of vanilla extract to the cream cheese, beating until fully combined. Gently fold in the 12 ounces of thawed whipped topping until the mixture is uniform.

Place half of the pound cake cubes in the bottom of a large trifle dish. Spoon half of the berry mixture (including juices) over the cake. Spread half of the cream filling over the berries. Repeat with another layer of the remaining cake, berries, and cream filling.

Cover the trifle and refrigerate for at least 4 hours, or preferably overnight, to allow the flavors to meld. Garnish with additional fresh berries before serving if desired.