Totally agree about the need of bigger brakes, but I never felt the need for bigger than 310mm discs + OEM 41mm pot caliper + Carbotech XP10 pads rears (maybe because I'm FWD, the rear is lighter), but I've definitely felt the need for bigger fronts. I've boiled the brake fluid so many times on track that I've lost count (RBF660, SRF), the rears were fine, but even the AP Racing 6 pot fronts have overheated.
Now I'm in the process of building some ducts.
Any way, as long as you keep the balance, the rears to have less braking power than the fronts, so you can induce some oversteer entering the corner (trailbraking), it is a nice upgrade.