Either way, switching to 99-04 GT style brakes, or 94-04 Cobra brakes, you will need:
Brake Calipers (2)
Brake Caliper anchor brakets (2)
Brake Rotors (2)
Brake Pads (box with 4 pads)
Hardware (4 bolts per side)
And I would recommend replacing the Front brake "soft" lines while you are upgrading, but it's not required.
The 94-04 Cobra Brake setup can be found for relatively cheap, sometimes around $200 for the whole sha-bang.
It's not as cheap as the 99-04 GT setup, like you said, but I can tell you from experience, putting the 13" Cobras on the
front was the best mod i have made to my car.