Well as an example Phat R33 and i have both just rebuilt and are putting big turbo's on RB25's and both went different ways about it, but both got our work done at S&D Bell Auto...
Im not giving figures of whats been spent by either of us but the questions to ask yourself is, what do you want to do with the car... IE; street driven, drag, track, drift, combo of a few etc
How much power do you want to make, and when would you prefer it to be made?
these sort of questions will determine what you do and do not need to do to get power out of the engine...
I could waffle on all day about this, but i will wait till you can answer more questions (and im sure others would like to have a say too)
maybe start a new thread about this?