What was stated above is great information, but to get 250rwkw you'll also need injectors.
A hi-flowed turbo has the potential to make 280rwkw, which is more than enough for a very quick street car.
I would recommend against using a 1bar actuator as it doesn't leave you much room to move. A hi-flow turbo is right on it's efficiency range using about 16psi, anything more it doesn't make much more power. When i had one fitted to my car it made 276rwkw@15.5psi, with cams and porting. So if you fit a 1bar (14.4psi) actuator, you eliminate the option to have a high and low boost setting. Having said that i never had a low boost setting, using this turbo, but my car was never daily driven.