I've changed from STi Brembos to 5570 330mm AP 6 pots for track use (now using PF discs and RS29 pads). Despite a slightly smaller total piston area they stop better and are more consistent. Best of all is the smoothness and progression and clean release that is just a pleasure to use. Call me sad but I actually enjoy braking as much as having a blast.
As Alyn on here told me, the truth is that the Brembo is a budget caliper and you get what you pay for.