..and with regards to discs, I think I will opt for new ones. And I am going dirt-cheap with OEM Brembo.
But instead of those for the BRZ I will get the part number from a 2005 WRX (26300AE061). According to a BRZ friend here, who is a hardcore Subaru enthusiast, those discs should be better quality then the part number Brembo makes for the BRZ/GT86.
They cost 38€ a piece.
If it turns out they are not up for the task, it's not much of a loss to replace them again.