I totally agree. I have Dr. Diff's 13" cobra style kit (2 piston calipers) on my Duster. It was a HUGE upgrade from my previous set up, which was already the later 11.75" mopar rotors. And even those were a noticeable upgrade from the stock 73+ disks. I still run the 11.75's on my Challenger, they're good brakes and it stops well, but the 13" rotors are far better.
I haven't run the 13" Brembo (4 piston) kit from Cass, but if it's better than the Cobra kit it'll be quite a brake set up.