You shouldnt really need to upgrade your uppipe since its already catless. Some headers do come with an uppipe though. I had to change mine because my factory one was jacked up when I was swapping turbos also.
the point of an external wasegate is not to gain power. THe point is to have a superior/safer system of controlling boost, especially boost spike associated with 2.5 motors and small turbos. Huge noticeable gains in boost control and power delivery are noticeable on even a stock turbo. IMO the only reason NOT to get an external wastegate is the loudness issue/police attention, other than that they are better in every way