300rwkw is about the 'piece of string' mark for these motors, IMHO. They do it and are known to do it reliably, however it is at its fair limit for a reliable motor.
The above is a fair example for the feasible and reliable maximum to be expected from it. Beyond that there will be compromises where you need to pick two from the list (cheap, fast, reliable).
For myself redoing the RB25 story, I would have a Hypergear SS-1, fmic, TBE, bosch, injectors, z32 and ecu. Expect 250rwkw as a max and excellent torque/response.