You already have - 10psi actuator, Pod, FMIC and Exhaust.
You may need - Fuel Pump.
The Midrange Flatness will be the biggest improvement and yeah the Topend numbers will be better but only to a point.
I would be interested to drive a setup like that to see the difference.
My SAFC2 got me to 192.4kw and the midrange driveability is very noticeable compared to stock.
The benefit of a Nistune would be the option to retune for more power with more supporting mods down the track.
ie. injectors and Hiflow etc. (SAFC won't really do this)
I thought the gains would potentially be greater than that for just a Nistune and tune though.