I don't think you need a 3" exhaust unless your aiming for 400bhp
You would be fine with just an Ecutek ecu remap although Simtek's sound nice as they do away with the troublesome MAF plus you can have a launch control and anti lag added.
Im pretty much standard now MY99 RB5 and have booked mapping for May and am fitting
A VF23, FMIC, FPR (already have full 3" de-cat), 3 port boost solenoid.
I should hopefully make about 330BHP
I think your standard turbo is ok for this sort of power
Alcon 4 pots are fine
I have fitted BC coilovers, whiteline anti roll bars, anti lift kit and uprated drop links and it has helped the handling no end
Hope that helps
Ciaran