You're right! Expensive and more complicated too

Welding a pipe on the original manifold for the external waste-gate seems nearly impossible. Plus, you have to cut the original T25 flange and weld a T3 flange... hard job i think too

Matty, Jari, Flea and plenty of people have proven now that GT3071 and GT3076 internally waste-gated are a good choice on our 2.0 litre.
If you want 430 HP i think you can go with the 3071R but you'll need headwork + hard boost to achieve this. With the 3076R you will have 430HP "easily". Don't forget you will have full boost +/- 500 RPM later with it.
It depends on how you want to use your car. Daily driving or "beast of the week-end"