hmm i think you can fit Mitsubishi EVO calipers on the tC. you have to create your own fit kit though. i dont remember if its Evo IX or Evo X calipers. not worth the hassel though.
just get new brakes all together. Brembo big brake kit in the front and Brembo slotted rotors in the rear. or get the Celica GT/GTS big brake kit for the front, because the front brakes on the tC are the same exact ones from the Celica, so any front brake assembly from a Celica will fit a tC, rear is slightly different... but there really isnt any interchagable parts between cars outside Toyota. and even in Toyota there arent many interchagable parts. Camry and tC engine are different, as well as transmissions (not really "different" but the tC's is a variant of the Camry's).
changing the front bumper on the tC is dumb in my opion. no great bumpers for the tC. heres a couple thoughts, either the Toyota/Scion front lip, or the Fivw Axis front lip with a APR front wind splitter. theres also the RS1 front lip. dont like replacment bumpers for the tC, they are either ugly, boring, or ricey.