You do NOT need anything for Stage 2 other than a Decent intake.
I only had CBE and it made no difference to the output at all.
The reason people recommend downpipe, Turbo Outlet, HPFP & intercooler is just to make things run better and help the system.
Intercooler won't give you more power but it will make that power consistent. I.E on a RR you will consistently see the same result after several runs whereas with OEM you start to suffer heatsoak so lose power.
Turbo Outlet will give you about 5bhp and around 8-10lb/ft
HPFP is ONLY needed if you get Fuel cuts at Stage 2. Otherwise it is only a requirement for Stage 2+
Turbo Downpipe is ONLY needed if you want more power at Stage 2 but again is a requirement at Stage 2+
If you go to Stage 2+ then you NEED:
Turbo Down Pipe
Intake
HPFP
as a bare minimum
I would recommend though adding
Turbo Outlet Pipe
Intercooler
Regards the intercooler don't be fooled by any marketing ploy the S3 cooler is more than up to the job for any K03 application and is a damn sight cheaper. APR or others are only needed really for Big Turbo applications.
Carl