Upgraded brakes?

You cant think about upgrading calipers unless you change the rims. You can surely change out the lines and pads. Eradispeed (by Baer) makes a 14" DRILLED/slotted rotor that is a direct replacement for the rears (with stock calipers), and with better pads will stop a little better. You would need to change the front rims though if you want to go bigger there. You can get the Brembo package that the cars come with for about $1200 or so. I will be going with the Baer 6-piston calipers with drilled/slotted rotors for about $1900, hopefully in Feb. Hope this info helps...let's see some pics of the car.
RC

I would get a set of slotted rotors (not drilled) of some sort and probably Hawk HPS pads, unless your going to auto-x or road coarse the car then you need something better. I just read a comparison of HPS, and Yellowstuffs, (I think there was another as well, but can't remember what it was). The Hawks were the best until the 3-4 hard stop and then they faded and the Yellowstuffs stayed more consistent, but if it's mostly just for street use you shouldn't have issues with brake fade. Also, definitely get some stainless brake lines, but I can't recommend a specific brand.