You could also consider the Racing Brake 4-pot front caliper upgrade (~$1100).
I have a big review here:
Its stock size, but the calipers are light (they say about half the FHI Iron 4-pots) and their rotor design is top notch.
I get pad fade now since i am running HPS, but the rotor and caliper are unfadeable to this point.
You can also stage yourself up to a BBK in the future if you feel the need.
Basically, when it came time to buy new rotors, you could get larger rotors + the caliper bracket and be in business.
You could also step up to their stock size 2-piece rotor, which is very well designed.
Their caliper uses a good pad design that allows you to get pretty much any compound you want.
Racing brake is also developing a rear bracket to allow a bigger rotor with the stock caliper.
P.S. I have driven a car with the Brembo GT2 front BBK. And it definately kicks ass... This is just another good budget concious option.