get the rb26dett engine with the 4 wheel drive conversion,
cheaper and u'll have a lighter body.
thats what i'd be doing, better then spending it on your rb25dett,
to get up to the power your looking for u'll need,
aftermarket ecu (2k),dump pipes (300) , bigger turbos (4k),pods,frnt mount (1.5k),exhaust (1k),pod filter (200), (ebc - lets say avc-r (900), thats just performance wise then u'll want stuff like boost guages (90) and so on, also aftermarket supension (1k) and the list goes on.. dude thats almost 10k.
if you get conversion you can sell the rb25det and get say 3k for it and then you can do some mods to the rb26
at the end of the day its upto you.
you could always give me the money i'll spend it