A T04Z is a 600rwhp turbo, bad choice for 400rwhp.
I suggest you really do some more reading.
Go through the RB25 dyno results thread. You'll see that it's a fine line between power and reliability.
Most people over 280rwkw have built motors, or are on E85 (upto around 320rwkw).
300rwkw is a realistic limit for a stock RB25, should last many years. A GT3071 or GT3076 would be your best bet - Use the search are there are many 5-10 pages threads on that specific turbo selection with more info than you'll ever need.
I'm a function over "wow". No point having the "wow" and only 400rwhp car with handling like a boat.
Better off saving your money on costly "wow" setups that offer nothing, and making worthwhile modifications and have a 400rwhp car that will drive like it's on rails as handling/suspension/brakes will cost the same, if not more, than the power modifications.