First of all - buy front 1.8 front calipers, rotors and rear rotors, calipers, handbrake cable, hub. Make sure it's same PCD. And before you go and swap them make sure it fits your rims.
Usually buying front and back together is cheaper than buying each one separately. Also consider swapping out master pump and servo.
But the question is whether you really need this upgrade or not. Stock power right now it's not beneficial to upgrade.
Personally I'd consider handling upgrades like suspension, antiroll bar, PU bushings first. Oh and Racetech's CAK.